7D Telephoto and Close-up lenses
Chris R-UK wrote:
Canon 55-250 IS
Canon 70-300 IS (not the DO version which is much more expensive)
Canon 70-200 f4L IS (outstanding lens)
Canon 70-200 f2.8L IS (standard professional lens)
Canon 100-400 L IS (wildlife lens)
Canon 200 f2.8 L (good for sports but no IS)
Canon 400 f5.6 L (widely used for birds in flight but no IS)
There are many other Canon 300mm to 800mm but they start to get very expensive.
I haven't included third party lenses (especially Sigma) and I have probably left some out, but I am sure that other posters will make further suggestions.
All of the lens in Chris' list are nice & sharp. With the 7D, you can pixel peep and tell the difference between the pretty sharp (e.g. 70-300) and the very sharp (70-200 f4L IS). Only you can judge what is good enough for you.
IS is nice to have on a long lens. You may not need it for outdoor sport or bird in flight. But most people need it for stage show or bird in tree.
AF speed is important for following action. In this case, L lens with ring USM are the best.
WYSIWYG - If you don't like what you get, try to see differently.