I've been asked to post up all the practice maps/servers that I know of, so here goes!
tr_airshot_v0 : http://www.gamebanana.com/maps/64670
tr_walkway : http://www.gamebanana.com/maps/107794
These are must-haves, you can read up on the installation/features on the gamebanana links.
Servers (I will update this list as I learn of more)
MGEMod Dallas - 126.96.36.199:27015 (24-slot)
MGEMod Chicago - 188.8.131.52:27015 (24-slot)
MGEMod Netherlands - 184.108.40.206:27015(24-slot)
MGEMod Australia - 220.127.116.11:27050;password dm
These four servers are purely 1v1, and allow you to practice your prediction, movement, and airshot skills. You'll see a LOT of extremely good players here, as there's usually at least 1 or 2 invite-level players on in the evening.
SOAP TF2DM Chicago - 18.104.22.168:27015 (10-slot)
DM-mod is tf2, minus anything other than killing. Insta-respawn, teams of 5, class limitations of unlimited scouts, unlimited soldiers, 2 demomen, and 1 sniper. In addition, sniper bodyshots do 0 damage, and jarate is disabled. Very good for simulating actual game scenarios; however, don't get angry if you get killed "unfairly" by groups of people. That's just how it happens.
Hope these help!