My sister has a D40 and so far only has the 18-55 kit lens. She's going to be heading to Africa in a few weeks and is looking to take some wildlife photography. Now the obvious choice of cheap(ish) telephoto lens would be the new 55-200mm VR, but I'm a little concerned that might not give her enough focal distance. The Nikkor 70-300mm VR is the next step up but is unwieldy with the D40's small body and perhaps a little pricier than she would like. Sigma has a couple 70-300mm HSM lenses that are worryingly cheap and lack image stabilization. Tamron just came out with a 70-300mm as well that's similarly priced.
Your thoughts? Anyone know of links to good review of these lenses, particularly the Sigma and Tamron?