Tripwire Interactive announced the next block of free DLC for killing floor yesterday (evening uk) entitled "level up", which gives some clues to what it will add but there will be "scoop" on IGN on tuesday that reveals all the new addtions.

News item here

However, there is an ad tripwire have placed on another site that totally gives the game away and that can be found here in the small ad on the right that starts off with the biohazard symbol.

New features:

- Perk level raised to 6
- 1 new monster
- 7 new weapons!
- 1 new perk (which will be demolitionist or some such)
- 3 new official maps

Couple all that lot with a free weekend to try the game

Eat your heart out valve!