I got a Dark Vengeance box recently so I could use the Dark Angels with my Space Wolves, but after reading the history about them it made me think.
Can I use Dark Angels with Space Wolves?
Yes you can. Wolves and Dark Angels are qualified as "Allies of Convenience" under the 6th edition allies rules. This allows you to field 1 HQ, 0-1 Elites. 1-2 Troops, 0-1 Fast Attack, and 0-1 Heavy Support options from the Dark Angels codex with your Space Wolves detachment.
In game-play rules they are treated as enemy models that cannot be directly target by your weapons and abilities. The DA troop options do count as scoring units for you though.