Not quite classed as a telephoto lens, but with a greater focal range than most standard lenses, the Tamron 55-200mm is a good all purpose addition to your kit bag. Tamron produce lenses for a number of camera manufacturers, and this lens is available with either a Canon, Nikon or Sony fitting.
Where do I even begin with this lens? I bought it new with my Nikon D90 and have been using it for almost 7 months now. I bought is specifically to help develop my composition skills. Since it’s a fixed focal length (prime lens) you’re more or less forced to walk your way around your subject to get that frame just the way you want it. Of course it’s a 50mm lens but if you’re mounting this on a DX format camera (like the D90 for instance) it becomes a 75mm with the crop factor considered.
Tamron produce lenses compatible with many camera manufacturers and the Tamron 70-300mm telephoto lens is a good example of a multipurpose lens suitable for those on a budget. It weighs 435g, which is lighter than the majority of competing lenses from other manufacturers which have the same focal range.