NOV is ex-div on 1/29/13. Does this mean I get the dividend if I own it at end of business on 1/28/13 (and therefore for part of 1/29/13) or do I need to own it at end of business 1/29/13? I think it means the former but it seems odd that it goes UP rather than DOWN after the dividend is committed.
The former is correct. The dividend does have an effect on the stock at the start of trading on the 29th, but in NOV's case it is very small and usually immaterial. Large percentage dividends have a much greater effect.