I'm sure that there are many more 29'er and 'cross tires besides the ones that Nashbar sells. Check PerformanceBike.com, HarrisCyclery.net, your LBS, etc. 29'ers are a growing market, so there will be new models coming out soon, I'm sure.
PS- If you think of going for wide 29'er tires, check to see if your rims are wide enough to handle them well:
http://sheldonbrown.com/tire-sizing.html#width
If you put a too-wide tire on a too-narrow rim, the tire will squirm a lot and you won't enjoy it
