My husband lost close to 60 lbs over the last year with a flare and getting really sick. His dietician suggested crackers with cold cuts on them as a snack as well as peanut butter etc. The protein helps build your muscles up.
There's also a Soy yougurt that Giant supermarket sells that's over 200 calories and doesn't taste that bad.
But I agree with everyone else, try to eat lots of small meals. Definitely take some time to find some foods you really like to eat. It made the difference with my husband.
He was 165-170 and was down to 115 three weeks ago. He's 145 right now but I think 15-20 lbs of it is water retention from the darn Prednisone. He's also hooked up to TPN via IV for 20 hours a day which works wonders with gaining weight because he's getting 1500 calories without eating a thing.