hmm really depends on your skill level, but some great beginner maps for soldier are rj_rckteer and jump_rush
If you are a little more advanced, jump_propel and rj_rckteer_adv are a lot of fun.
For demo there's a ton of good maps. endurance is good, my maps hobo, bob, hobo2, rush are all good demo maps. ice2 is great for learning how to pogo.
you can also find a lot of good maps playing at the tf2newbs jump servers. They got a long nominate list of all the best jump maps
tf2newbs.com
server#2: 113.212.76.6:27075
server#2.5: 113.212.76.6:27135