Originally posted by lokstah
Oh, the occasional rain ride isn't the end of the world.
Riding on wet roads (whether its raining or not -- arguably, actually, the problem is greater when it's not) tends to kick a lot of grit-laden water and sludge up onto your bike. In general, grit and grime is the number one enemy of happy componentry. It's little bits of dirt which contribute to wear, so by all means, clean your bits and pieces after a wet ride. Not the end of the world.
The other thing to be wary of is water entering and compromising sealed or semi-sealed parts containing grease and close fitting parts, like bearings. Hubs, headsets, bottom brackets and some pedal designs are typical examples. Frankly, once those parts are assembled and properly installed, the only way to insure that they aren't compromised is to minimize their exposure to heavy doses of water. That, and hope luck is on your side. Sometimes, if you're ridiculously unlucky, a sprinkle from your water bottle can muck up a hub -- but generally, you can ride through any number of rain storms with no real problems.
In the end, most water-senstive components are either hardy enough to withstand reasonable conditions, or they're reasonably easy or inexpensive to service should they require a re-greasing or overhaul. Avoid the Gulf Coast during hurrican season, but don't sweat it if you feel like riding in the wet now and then. As always, keep an eye on your stuff and treat it respectfully, and you should be fine.