There are literally thousands of sites out there! The web - to me the modern equivalent
to the famous library of Alexandria - has huge amounts of information but it is uncontrolled
and often opinionated.
Try typing in a specific condition but remember the above caveat.
Potentially useful links
"Getting information off the Internet is like taking a drink from a fire hydrant." Mitch Kapor.
http://www.cobfoundation.org/ The Cystitis and Overactive Bladder Foundation. Provides information and support to sufferers of bladder problems, including Interstitial Cystitis, Bacterial Cystitis and Overactive Bladder.