Achievements Beta 2
Helps you with achievements or if you have them already, training against specific infected.

Green Screen
Fun map that's all green. Good for character screenshots.

Hunter Skeeting V2.5
Good for training to skeet or melee hunters.

Bedrooms 3: Bitesize
Cool survival map where you are super tiny. (So are the infected)

tr_unnamed_b2
The only training map I've found that includes a basic horde training area.

Training Witch V1.1
Good map for witch crowning. Start with 1 witch, work up to 3.

Suicide Blitz
A full campaign/versus which includes 3 survival maps. High rating and good feedback.

Death Aboard V7
Not a bad campaign. Some mapping problems but otherwise good.

Hunter Training V2.8.1 (VPK version)(This map was pulled because it messes things up too much)
Another training map for hunters. More involved than hunter city, but less enjoyable.

Coal'd Blood V7
4 Campaign and Versus maps. High rating.