1. The Vanbrugh String Quartet (http://www.rte.ie/music/vanbrugh) An easy winner of the "most music" award, this site has a wide choice of sound-bites from the Vanbrugh's acclaimed series of Beethoven recordings which download quickly and play with crystal clarity. The site uses RealAudio.
2. Christ Church Baroque (http://indigo.ie/~cccdub/music/music.html) Everything you might ever want to know about music in Christ Church Cathedral, Dublin, and then some; this is a bright, user-friendly site with mind-boggling amounts of information on choirs, organists and the cathedral services and cheeky little colour graphics - but no music.
3. Dublin Chamber Music Group (under Arts - Classical Music at http://www.browseireland.com) Despite the numbing MIDI-manipulated background music, this is a good lively page with plenty of hands-on activity to interest chamber musicians including residential weekend courses and monthly sessions in members' homes.
4. Opera Theatre Company (http://www.imn.ie/otc) "Crashing waves, rising tensions, descending fog, spiralling paranoia": to be found in OTC's own description of its current touring show, Peter Maxwell Davies's The Lighthouse. Good colour pictures - but no music.
5. Operaweb ( http://www.opera.it/English/OperaWeb.html) For a lighthearted look at matters operatic, including the longest recorded operatic breath, which was apparently taken by the tenor Alfredo Kraus, who held the final despairing "Ah! Manon" from Puccini's Manon Lescaut for an astounding 25 seconds.
6. Tenorland ( http://www.geocities.com/Vienna/1450) Cool name, and lots of info about tenors, mostly of the dead variety; if you're into Caruso and co., you'll find comprehensive biographies and sample recordings, some of which are historic recordings sounding as spectacular as ever.