Orcs must die 1 is on sale this weekend for 1.74euro and I guess something similar in $. ( 75% off )
If you own OMD!1 on steam you will get 10 co-op levels from the first game in OMD!2 If you think you are gonna buy omd!2 you could think of this as dlc with a whole game as a bonus!
Orcs must die! 2 is released on monday, and a steam demo is out now (well the download doesen't work for me yet)