Plastic gallon sized bag for my seat when it rains because I HATE being a soggy bottom boy...
I'll remove the arm pads on my aero-bars to keep them dry as well some times.

Something I've noticed though, if I'm driving in the rain (like on the highway), the parts of Fritz that don't stick up over the roof of the car stay dry. So if I happen to be traveling on the highway and pass through a shower, only the seat and handlebars get wet. Of course, if it's stop and go in the rain, then the whole shebang is getting it, which is a TOTAL bummer but I stopped treating Fritz like he was precious long ago...

/poor Fritz
//he's not precious