My husband has a couple bamboo t-shirts that he bought from a web site specializing in all sorts of bamboo products. This morning he got a message from their mailing list stating that they were now carrying their own line of bamboo yarn. Granted, I've never worked with either this brand ("Spun Bamboo") or South West Trading's version, and this new brand only has seven very basic solid colors, but it might be worth checking out for people who didn't know if they wanted to spend $13+ on a skein of SWT.
The skeins are listed as having 280 yards and a gauge of 5 st/in, which should be comparable to SWT (30 more yards, in fact). They're selling for 9 bucks, AND the company offers a 20% discount on bags of ten. Sounds like a deal.
Web page here.