I have long hair and it gets reasonably sweaty/damp, but I usually just put it up for the rest of the day (hair in experiments=bad)-- I've also found that if I put it in a loose bun for an hour or so it dries out and I can put it down and it looks ok (but I am also blessed/cursed with really straight hair no matter what I do to it so it doesn't get wrinkled/crazy being up for a bit).

I'll sometimes extend my ride home by taking a longer loop, but other than the very occasional run to the grocery store (1 mile...) I don't think I've ever gone for an after-commute ride (but my round trip is 22 miles). If I know I'm going to ride on the weekends, I'll usually take a day off during the week (usually Friday), but honestly the vast majority of my miles are commute miles-- I like to sleep in on the weekends, plus my fiancee works evenings/nights so Sat/Sun mornings/lunch are some of our only reliable time together during the week and he doesn't ride much (we occasionally toodle around the neighborhood, but that's it), I suppose I could ride in the afternoons/evenings on the weekends, but I haven't found a group that does that and I can/do ride by myself everyday on the commute, so that idea doesn't seem all that exciting.