Most of us who work for a salary have (or should have) 401k's. Now, obviously, the old advise was to contribute to it as much as you can. And I think it's still a valid advise. The problem I always had with my 401k is that is so overpriced. Even index mutual funds in it had an expense ratio of at least 0.25%, while the same can be had for 0.17% if you would go to, say, Vanguard. Oh well, I thought, that's a price of having a 401k with the 401k provider (which is one of the bigger ones, too).
However, recently several big players started offering( gulp..) ETF-based 401k. ShareBuilder, for example (which merged with ING not long ago). With ETF-based 401k potential savings on expense ratios, 12b-1 fees etc. etc. are just mind-boggling.
So if switching from traditional mutual fund-based 401k provider to ETF-based one is a possibility, I would grab it!