I've done lots of short ones (~weekend length or so) - I'm leaving for Maine on Saturday, as a matter of fact. The two longer ones have both been automotively-inspired.
First was a blast down to South Carolina (~1500 miles round trip) for a vintage BMW event; I own a 2002 (model, not year) and it was 02/02/02, so the factory threw a party for owners from around the country. Hell of a drive in February in an almost 40 year old car with a built motor and track suspension.
The other was seven years later, when a buddy and I joined up with another group of like-minded car people to do a banger rally, known as Big Apple to Big Easy, or the BABE for short. Five days to get from New York to New Orleans in a car costing no more than $500. The route included very few highways, so we ran all over the place, including a run through the infamous Tail of the Dragon at Deal's Gap. Stayed one night in NO, then up to another friend in Atlanta, overnight there and back to NY the next day. Great and utterly exhausting trip.
I'm overdue for another big roadtrip. I'm thinking cross-country, or at least the western half. Maybe via Route 66 or the Lincoln Highway. Time to start planning....
Oh, and no photos other than some boring documentary shots from the earlier trips, but here's a gratuitous photo of the 2002 (which I still own).