In addition to total averages, I've also include averages of the reward checking accounts based on the year when I first reported on it. This is intended to give some indication of how well the rates have held up. I first reported on 86 reward checking accounts in 2007, and these accounts now have an average yield of 5.14% APY with an average balance cap of $39,826. As you would suspect, those that I first reported on in 2008, have an higher average yield (5.51% APY). This is an indication that the initial rates are a bit of a teaser. However, there is not a whole lot of difference between the two. I reported on 4 reward checking accounts near the end of 2006, and these have an average yield of 4.67% APY. This is probably not enough to draw too many conclusions.
I also compare the average rates and balance caps between banks and credit unions. The reward checking yield average from 50 credit unions is 5.35% APY which is just above the average from the 99 banks (5.24% APY). Banks have the advantage on the balance caps ($38,182 vs $32,100).
I also have statistics from the 12 institutions which allow people from any state to open reward checking accounts. One thing that stands out is the difference in rates between those I first reported in 2007 vs the ones in 2008. The average yield for those in 2008 is 5.84% APY vs 4.59% APY in 2007. So for high yields, you're better off with a local-only reward checking account.
It should be noted that I probably have many rates that are out of date. I've been updating many over the last week, but with 149 institutions and with rates changing so fast these days, it's very likely that a few are still out of date. If you see any rates that have changed, please leave a comment in the post of that institution.