So...the rain has been getting me down. Are there any fenders that work well, and can be EASILY tranferred from bike to bike? I'd like to be able to unclip and clip to another bike, much like moving lights from bike to bike.

Get one of those rear fenders that attaches to the seatpost. It's enough to keep you from getting skunk stripe, but it's not as if it's a full coverage fender or anything. Up front, get a clip on that attaches to the downtube.

Crud Catcher clip on fenders

*edit*
looks like they haven't updated their site for a while, but their stuff is still available online at a few retailers.

It depends. Road bike? Mountain bike? Hybrid? Cruiser? What sort of bike?

I bought these in black and I'm pretty pleased. Attaches with a screw-cog like a lot of lights. Haven't used the front one yet, but on an 8 mile spring commute the rear kept all but one splatter off my back. And I think that's only because it swings a bit, so I'm just gonna stick a rubber strip in there (don't know why it didn't come with one) and it'll stay put better. They're really easy to transfer bikes. Also, they're better looking than most of the plastic space-agy ones.