Now the proud owner of a Canon 400d - I was wondering whether it is worth upgrading anything from the start. The standard lens, perhaps? If so, what are my options?
I'd check out some of the other threads on this subject. I personally think the 50mm/f1.8 lens is something most Canon users should have on hand, especially considering its low cost.
A Nifty Fifty is nearly a must-have in any photographer's kit. Beyond that, any other lenses you purchase should be tailored to the kind of shooting you intend to do.