SQL2005 Books Online was pretty awful at RTM, and I've just seen that MS have released an updated version already. You can get it here:

It's something of a stealth release - I only heard about it while browsing Channel 9, not from any of the other SQL Server-related rss feeds I read. You'd think they'd publicise this kind of thing better.

 

Browsing through, though, I can see that it still contains several errors - see, for example, the CALCULATE statement where various features are documented that were dropped from the beta ages ago. But in this case I only have myself to blame: a few years ago I met a guy who worked on SQL BOL and he pointed out the 'send feedback' feature that's available on every page - if you see a mistake then you can use this feature to send an email directly to the BOL team and presumably they'll try to fix it before the next release. Needless to say when I first saw this particular entry I didn't bother to send any feedback, but I have now and will make a special effort to do the same whenever I see any other mistakes.