I had the same debate before I got my first dSLR a few months ago. I liked the feel of the 30D ($1100), but in the end it was almost double of what the XTi ($670) costs online. I went to a show that Penn Camera had and tried both cameras out, using different lenses and with and without their respective battery grips. I ended up getting the XTi mainly due to cost; but got the battery grip to make the camera feel "fuller." After shooting many 100's of pictures around town and a cousin's wedding, I could have made a better decision. I got the SterlingTek batteries and can shoot ~1,000 pics on a set of batteries! Having a natural placement for the shutter is awesome for vertical cameras.
Lenses are not cheap, most nice glass costs ~$500 a lens. It reall depends on your budget. I've spent more than $2,000 for the body, three lenses, and various accessories. A easy telephoto recommendation is the Canon EF 70-300mm IS USM f/4-5.6 (~$550). Its easily one of the best non-L glass telephotos that produces very nice pictures. The "plastic fantastic," ie the Canon EF 50mm f/1.8 prime is a great, cheap ($80), open lens. For a walkabout lens, look into the Canon EF-S 17-85mm f/4 IS USM, the Tamron 17-50mm f/2.8, the Sigma 17-70mm, or if you have the money the Canon EF-S 17-55 f/2.8 IS USM.
Check out Yllus's thread as well for suggestions, it helped me out alot! Also check out the other photo sites in the Reference thread (photozone, FredMiranda, etc)