I would start with nuts and nut butters, if you're not allergic. Almonds, walnuts, pistachios, etc. have healthy fats and protein, and an ounce, which is not that many, has about 160-180 calories. Also, a protein shake or smoothie with protien powder mixed in could also be good choices.
"If you drop an egg, you don't say, 'Oh, shoot' and drop the other 11, do you?"
-Source unknown, but obviously brilliant
Reached goal 4/16/2010...but kind of afraid to look these days