ShareBuilder just sent me an email about 401(k) rollovers. If you roll over an account of $25k or more, you get a $250 bonus. A quick search finds that Schwab and TD Ameritrade might be offering bonuses as well - for instance for rolling over $50k to $99,999 one would get a $200 bonus.
It just so happens that I do have a 401(k) that could use some rolling over. However, I am not really a fan of Sharebuilder. Yet I do have an account there, so at least it would be less work than getting a lesser bonus from the other brokerages above.
I wonder if Fidelity of Vanguard would match the offer? Eventually I would like the account to end up at one of those two places. But, I guess that is true of most people, which is why those two don't have to offer such bonuses in the first place.