The last one now is of 20110602, which is fairly recent.
The autobuilds are not always created successfully. Updates on compilers or other toolchain changes might affect build successes. When these builds fail, they are not propagated so you'll have to "wait" a week (if you desperately need a build that's more recent than a few weeks old). Considering that Gentoo is a rolling upgrade distribution, working from a month-old stage is not an issue. Even several months old isn't an issue.
Wkr,
Sven Vermeulen