Fun is a worthy business topic for several reasons. On the one hand there is Google (NASDAQ:GOOG) --the stuffed gorilla in the playroom, the company that has single-handedly made volleyball the new dental. On the other hand are Dilbert, The Office, and other pop-culture arbiters that portray the average workplace as hope's Dumpster. A whole industry has sprung up around corporate play-together-stay-together programs: cooking classes, improv training, team drumming. These days you can't shoot a Nerf gun into a roomful of CEOs without hitting a self-proclaimed fun evangelist.

Plus, it's August. It's a little hard to concentrate.

With labor markets tight, business leaders understand that fun can tip the scales when all else is equal. Fun not only lures employees, it also helps them acculturate, which becomes more important as businesses become more virtual. And, of course, fun is associated with creativity. Not everyone can quantify the return on their Lego sets, their giant slides, their movie nights, their costume contests. Still, many of the companies you'll meet in the following pages have whipped fun into a froth of innovation.

But don't buy that karaoke machine yet. The common practice of treating sick cultures with a fun-graft--parties, silly hats, visits from Mister Softee--is insulting to employees and vaguely grotesque. For fun to thrive, meaningful work, competent management, fair compensation, and mutually respectful employees are table stakes. If you lack any of those, start there. Once the bread's in place, come back and we'll talk circuses.

Everyone else: On to the festivities.