A year ago, 2010, I was able to book Delta out of Logan for a good fare...can't remember exactly what it was, but my dd and I both flew r/t, nonstop, for under $450. But, you have to be looking at exactly the right time. I found the perfect flights/fares, and waited to double check with my dh before booking and 6 hrs. later the 'perfect' flights were gone. I had to fly on Monday and return on Friday, but 4 nights was better than 0 nights I guess.
Then, last April we flew DirectAir out of Worcester. I believe we paid about $140 pp, r/t. Booked a half price sale. We are flying in Oct, on DirectAir, using the Family Ties program....about $160 pp, r/t. I like DirectAir. My only issue with them is that when I actually booked our flights (bought the Family Ties vouchers way in advance), I was told by the CSR, that we would each get one free checked bag. But, now I'm finding that that wasn't true. So, it will cost us addtl, but we'll pack lighter to avoid those fees. Not happy being told something that wasn't true, but the CSR could very well have just made a mistake.
Otherwise, I fly out of TFGreen a lot. I get some decent SW flights. And out of Logan, I look for JetBlue, but seldom find any decent April break fares with them.