The section on fluorescence of the Olympus site:
http://www.olympusmicro.com/primer/techniques/fluorescence/fluorhome.html

Nikon's imaging and tutorial pages:
http://www.microscopyu.com/

Leica's confocal home page:
http://www.confocal-microscopy.com/website/sc_llt.nsf

General info about confocals from the home of the UBC imaging course:
http://www.cs.ubc.ca/spider/ladic/confocal.html

Interactive plotting of fluorescence spectra--very handy!
http://fluorescence.bio-rad.com/

The WWW Virtual Library of Biochemistry and Cell Biology, which has many useful links to microscopy and all things Cell Biological:
http://www.biochemweb.org

The archive of the Confocal Listserv, an email list for all confocal topics:
http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal

The home page of Universal Imaging, makers of Metamorph:
http://www.image1.com

More information about lasers than you could possibly want:
http://www.samslaserfaq.com