Just to round out the topic, I thought I'd let everyone know what I decided. And the winner is.....
Sigma 14mm.
Here's what I took into account...
1. timing - leaving in 8 days doesn't give me a lot of time to get everything put together
2. system support - S&S officially supports the 14mm, which means theoretically, if I buy the parts they list, it'll work (yeah, Murphy's law and all that). Neither the Sigma 15-30 or the Canon 17-40 have zoom gears available, which means custom parts before next week, which isn't going to happen.
3. budget - ok, this one isn't obvious since the 14mm is more than the 15-30mm that Bob recommended. BUT if you add in the additional stifferning rings that I'd need (2 of them) to get the 15-30mm just to fit the port then the 15-30 actually costs more.
4. angle of view - As James pointed out, the 17-40 is really more of a mid-range zoom lense when used on the D60. That's not a bad thing, in fact down the road I'll probably pick one up for that very reason, but for next week, I'm looking for wide...
The other logical alternative (thanks again James) is the fisheye. If I were looking just for reef scenes and pelagics, I'd probably go that route. As it stands though, I'm not sure I'll be able to get to Truk again soon, and I want to get as wide as I can without having to worry too much about whether the wrecks look like wrecks or not.
Anyway, thanks everyone for your input. Hopefully in a couple of weeks I'll have some interesting results to post...
Tom