This appeared yesterday in USAToday and it's such a pearl, I had to direct your attention to it.
His method of searching for group fares involves first looking for the number of fares in your group (say 5), getting a price and then clicking away. DON'T BUY at this stage. You then do another search for just one ticket, and if it comes out at a lower price, you add passengers until the price jumps up again. Then you buy some of the seats at the lower rate and some at the higher. Overall, your group saves. Pretty nifty eh? According to Seaney, it also works with groups as small as two.
To read Rick's original piece, click on the link above.