(Disclaimer - All prices are US dollars, since both Sue and I are in the US :-)
There has been a mention or two of a longer zoom lens on this thread. If you're considering a Canon zoom lens in the 70-300 range, there are two you'll see mentioned quite a bit - The 75-300 (older) and the 70-300 (its replacement). The 75-300 can be found for $150, while the 70-300 is about $550, but if you're considering one or the other, read this review : http://www.bobatkins.com/photography/reviews/ef_70_300is_review.html There's also a 70-300 "DO" (diffractive optics) model from Canon that is very compact, but it's also much more expensive ($1300).
There's also a 70-200 zoom from Canon in the same $550 price range with better glass, but as with all things there are trade-offs. I just bought a 70-300 and had to decide between it and the 70-200. If you're interested, here's what I see as their relative points (i.e., take this with a grain of salt since I'm no expert, but I've done a bit of research on it for myself) :
EF 75-300mm f/4-5.6 IS USM
Pros - Low price, Decent optically, but not great
Cons - It's been superceded; it's not bad, per se, but there are better lenses out there. Personally, I'd give it a pass. From what I understand, the "Cons" of the 70-300 also apply here.
EF 70-300mm f/4-5.6 IS USM
Pros - Compared to the 75-300, better optically; a tad lighter; better IS
Cons - The end rotates when focusing, which can make using a polarzing filter a bit problemmatic; can't use a tripod collar if you want that; the end extends quite a bit when zooming.
EF 70-200mm f/4.0L USM
Pros - Compared to the 70-300, still better optically ("L" glass is good); better construction ;can use a tripod collar (allows you to attach the camera/lens to the tripod at the balance point rather than at the camera) ;good resale value; nothing moves or extends when zooming, IIRC; I think it also has a "true" ring-type USM focus motor, which means if you want to focus manually, there's no need to switch it between AF/MF modes.
Cons - Makes you want to buy more of those expensive white "L" Canon lenses! Also, you have 100mm less focal length to play with, but it's all f/4 and doesn't change as you zoom.
By the way --
USM : Ultrasonic Motor; a better type of Canon autofocus technology
IS : Image Stabilization; Canon's anti-shake technology
Anyway, now you can tell me you're not considering a zoom lens after all!