I am technically an independent contractor, so I fund my retirement through a SEP-IRA (self employed IRA). So, instead of having money deducted from a paycheck and investing in a 401k on a regular basis, I put my money toward retirement throughout the year whenever I see a dip in the market (or simply whenever I have the extra money to do it).

I just put in $5000 today. I'd been waiting to see how far the market would fall. Even though I don't necessarily believe it's done falling, I do believe a roughly 14% fall in the S&P is enough of a signal to believe it's time to get some stocks while they're on sale. Not doing anything tricky, just putting the money straight toward a 500 index fund.

We're going through a tough economic time, but my retirement is still at least 20+ years off. So the money goes in now. Buy low, sell high and all that.

If you have the ability to time your retirement contributions at all, I'd suggest that now is a very good time to do so.