I have decided to buy a Nikon D5000 as my first digital SLR, can I have your recommendations of a good zoom lens for wildlife photography, priced up to around £500.
You'd probably be looking at a 55-200mm lens, although I'd recommend a Sigma or Tamron rather than Nikon's own as they seem to perform slightly better overall. You might be able to pick up a 70-200mm Sigma lens with constant f2.8 aperture, which would be excellent for wildlife photography, secondhand if you're lucky, and there are a few kicking around eBay for under £500. Be careful when purchasing lenses secondhand as perished seals can lead to mold on the lens, which creates spots of poor focus.
Do the Sigma lens have some form of VR built into them, and is this as important as people say?
VR is very useful because it reduces camera shake which can ruin your pictures (even a small amount will degrade the image quality) and enables you to shoot at lower shutter speeds without getting it.
The suggestion of the http://www.warehouseexpress.com/buy-...n-fit/p1027429 (or the http://www.warehouseexpress.com/buy-...n-fit/p1027468version) is a good one because both are superb quality lenses with fast maximum apertures, which makes viewing and focusing esier and faster, and enables lower light shooting. Neither has VR though and both are above your budget (between £600-700), though you could almost certainly find secondhand ones under £500.
However, I would actually be tempted to recommend http://www.whatdigitalcamera.com/equ...6-af-s-vr.html lens, first because it has VR built in, and secondly because 200mm is not really long enough for a lot of wildlife subjects. It's around http://www.warehouseexpress.com/buy-...-lens/p1014102. The downside is the relatively small maximum aperture which would in low light force you to use slower shutter speeds and, as a consequence, makes the VR more essential. Or you'd have to shoot at a higher ISO than you would with the faster lens.
You don't say what kind of wildlife you have in mind but for birds, African safari and many other subjects even 300mm may not be long enough, in which case you could look at even bigger beasts such as the http://www.warehouseexpress.com/buy-...n-fit/p1025303 or http://www.warehouseexpress.com/buy-...n-fit/p1025306, both of which are Image Stabilised. Again, they're both above your budget (up to £750) but you may find used ones.
Thanks very much for the advice Nigel, as being a newby to all this does get a little mind boggling at times.
I will be traveling to the jungles of Borneo to photograph Orangutangs some of which will be in the trees, I was thinking the 70-200mm f/2.8 sigma may be enough for this, but am still a little wary of purchasing a lens without OS or VR. Is camera shake a major problem generally or would it be more of a problem with longer lens. I like the thought of the f/2.8 but at the expense of the OS it makes it a tough decision.
As Nigel says, 200mm may not be enough for your chosen field.
As for the lack of VR, the f2.8 aperature will allow more light to hit the senso, allowing a faster shutter speed, and hence removing the need for VR in many cases.
If i had the budget for sports, I would definitely sacrifice VR for a fast, f2.8, lens. Both however would be great