I was thinking today it'd be nice if Google's awesome conversion stuff also did time zones. So I could google "7:30pm CST in EST", etc. I was kind of surprised it didn't work when I tried it this afternoon.

Yeah, I'd love this too. What you can do right now, as you probably know, is enter e.g. [time in san francisco], resulting in a onebox:

<<San Francisco, California, US — Current local time: 1:05 PM on Thursday, November 2
According to www.google.com>>
http://www.google.com/search?hl=en&q=time+in+san+francisco

We wanted to do this just the other day too. I assumed Google would have done it but it let me down...