The suggestion to get the camera package with the lens is a good one. The 18-55mm kit lens is pretty cheap, but is surprisingly good. You can only use it with certain EOS models because its an EF-S lens, but if you upgrade later from the 350D to the 20D or 30D then it will still work. But not with the big expensive Canons.
As for the longer lens........it all depends on how much money you want to spend. A great majority of shooters on
www.Fencecheck.com use the Canon 100-400 L lens. It's price varies, but is usually around $1400 US. Of course, across the pond you can get stuck with VAT and pay more.
Myself, I have a Canon 70-200 f4L and am going to get a 1.4 extender to make the lens a little "longer". My next bigger lens may be a Sigma 400mm lens, because I dont think I can afford a big Canon L lens.
Oh, and the L lens are the better line of Canon lenses. They are of better quality (contruction and the glass in them) and it really shows.
With the lenses you buy, you want to make sure you cover the whole range of zooms if you can. For example, my first lens was a 28-135mm lens, then I got the 70-200mm. So I have from 28mm to 200mm covered (good quality lenses). Then I will extend the 70-200's focal length with the 1.4 extender when I get that.
All in all, if you are serious about a DSLR, get the best glass you can afford. Dont skimp because you will end up paying for it in the end. Happy hunting.