Want to get something off your chest or share your life with the world? Join the growing ranks of online diarists, writes Anna Carey

Rob Rummel-Hudson lives in New Haven, Connecticut, where he works at a university hospital. He's married to Julie, and they have a sweet, funny little daughter called Schuyler. He has several pets, plays the trombone, doesn't like George Bush and is very funny. I like Rob a lot, but I don't know him. I've never met him, and I probably never will. I just read his diary.

Every day hundreds of thousands of people all over the world, from celebrities like Moby to bored 16-year-olds in Dublin, write about their lives and put the results online. Unsurprisingly, many online journals are unreadable, and one suspects that many of their teenage writers will be cringing in a few years. But the good ones are compelling.

It's very easy to join in. Anyone with Internet access can start an online journal, thanks to sites such as Diaryland.com, which enables users to start simple Web diaries for free. Even more user-friendly is Livejournal.com, which offers a more community-oriented service. "Journalers" can add other users to a "friends list", which encourages communication between diarists. Write about a problem or issue in your journal and you can get sympathy and advice within minutes.

That's just one reason why so many people write online journals. Some of the most interesting, readable diarists do it because they love writing; they want to entertain, and the minutiae of their lives offer rich pickings for entertainment. Some write for the same reason people write private diaries: to vent their feelings and document their experiences.

When Sarah Ryan, a student from Limerick, was studying in Germany, her journal kept family and friends informed of her doings. "My dad used to read it to keep in touch with what I was up to," she says. "A few months before I went home I got a bit homesick and just didn't get up that day. I posted it in my journal the next day. That evening I got a phone call from my dad and a few days later a package [arrived from home\] with some chocolate and a cute little card."

For other diarists it's all very logical. "I wanted to record stuff, moments in my life I call snapshots," says Lynne Ann Morse, a Dublin-based diarist. "Whether others would read it or not was something I decided to leave to the fates. I would just commit to writing."

For some it's a writing exercise. "I decided to start an online journal as a discipline, to make sure that I wrote a readable piece every day," says Helen Finch, a 27-year-old from Kilmacud, in Dublin. "I'd kept journals in the past, mostly in my most angsty teenage years, and the results were sporadic, turgid and deeply embarrassing. By contrast, because I know that, in theory, anyone can read my online journal I try to force myself to write engaging, well-composed pieces which do not solely refer to myself and my particular woes of the moment."

Rummel-Hudson became a diarist almost by accident. A well-known figure in the online "journaling" community, he's been sharing his life with the world since 1997 - a very long time in Internet terms. His journal, at www.darn-tootin.com, is smart, funny and often touching. "I had done some other Web projects, like a facetious page about my home town and some essays on random topics," he says, "but the idea of actually keeping some sort of journal didn't really occur to me until I found myself writing these essays in a more regular timeframe, like maybe once a month, and the topics were becoming more personal. Making the transition to an actual journal just sort of happened."

Pamela Ribon is a journaling legend whose recent first novel, Why Girls Are Weird, was inspired by her journaling experiences. She set up Squishy (a.k.a. www.pamie.com) in 1998, and what started as a series of observational columns turned into a journal when she "realised my daily life was much more entertaining". Thanks to Ribon's sparklingly funny writing Squishy soon became enormously popular, even spawning an online community of Squishites after Ribon set up forums on the site. But in 2001 she shut down Pamie.com when running the forums became financially prohibitive and running the huge site became emotionally exhausting.

"I wanted some time to devote to writing without the pressure of talking about my daily life," she says. "I was going through some changes in my personal life that I wasn't able to share with people, and not talking about those things online felt dishonest. I needed to re-evaluate my responsibilities to the audience." She restarted the site without the forums last year, after getting her book deal. "I told myself that if I sold the book I could come back to the Internet on my own terms to talk about whatever I wanted, when I wanted. So I did."

Like Ribon, many journalers find themselves reluctant to ignore certain issues in their lives but are equally reluctant to tell the world about them. Livejournal.com offers diarists a way around this by allowing them to post restricted-access entries, which can be seen only by certain people. Nine Declare, a long-time journaler from Holywood, in Co Down, has found the service very useful. "In the past it was a bit awkward sometimes, because I might be faced with writing about something I really needed to get out of my system - a break-up, say - and wanting to be authentic about my feelings instead of just glossing over it, but I'd have to consider also what the other person might think if they read it," she says.

Rummel-Hudson has always been pretty open in his journal, but he learned the hard way that sometimes he should think before he types. "I've inadvertently revealed private information about family members that got them upset with me, I've gotten fired from a job and I've written things in anger that I definitely regretted. I think I've got that balance now, although I suspect it makes me a little less interesting to read."

Most diarists find opening up to the public to be a mostly positive experience. "I never expected to generate readership, nor to get so hooked on other people's diaries - but I have, and I'm delighted," says Helen Finch. "There have been next to no negative effects . . . apart from all the time wasted online, of course."

These good vibes can be infectious. This spring public libraries in Oakland, California, lost much of their funding and were in dire need of books. They set up an Amazon.com wish list, so concerned locals would know which books they needed. They didn't expect to get books from Ireland, Canada and Japan. But when Ribon wrote about it her readers responded in their hundreds. "This is the closest thing to magic that I've ever seen," said Oakland children's librarian Jamie Turback, who described the arrival of more and more packages as "like a sequence out of a James Stewart movie".

Ribon is modest about it. "One of my new year's resolutions was to get active with a charity or a cause, so I suppose I reached that goal," she says. Inspired by the Oakland book drive, Pamie.com readers have also been donating books to libraries across the US.

So writing an online journal doesn't mean you're self-absorbed. And it's not the literary equivalent of appearing on Big Brother. Even the most honest journalers reveal only aspects of their personalities and lives. Diarists agree that they keep unwilling friends and family out of their journals, and their lives are still their own. "While I do write a lot of reasonably personal content, ultimately [my journal self\] is a persona," says Helen Finch. "Just because they read my diary doesn't mean they know me."