Were the layoffs across the board or specific to a practice group or office?
This is really the key question. No firm in their right mind would lay off bankruptcy attorneys right now, but M&A, real estate and lending is in trouble.
Also, even if there are layoffs in litigation and other busy practice groups, it's possible that a firm was "cutting the fat" and getting rid of lower and midlevel associates who just weren't cutting it. Usually these people stay with the firm FOREVER and if they're ever asked to leave, they do it quietly and give the person a crap load of time to find other work. So if you have attorneys who suck, it's a perfect time to cut them loose and blame the economy and still not look like a bad guy (which plays into job decisions re: which firm seems like a "better" place to work).
So I wouldn't panic yet about a firm no-offering an entire summer class. But I would plan on working my ass of this summer, both in the work you do (making sure it's PERFECT), and in getting to know people and being well liked by everyone. (tip: don't focus on schmoozing *just* with partners - partners often ask younger associates they work with often for their opinions on your work and personality)