Nikon lens slr camera?

What's a decent lens for a slr camera? Is a 70-300mm good for sporting events?

SLR cameras these days are good. But for sport, you may need a camera which have a high continous burst shot. For Nikon, get Nikon D90 or D7000, or higher if you want better quality.
oh yes 70-300mm is good focal length.

Apart from telezoom reach, action events need a fast (f/2.8) lens, all the vibration reduction (VR) you can get, as well as fast and reliable AF. Nikon 's 70-300 mm only has f/5.6 at the 300 mm end, which may just be adequate under the brightest of circumstances, but will let you down in less favourable lighting conditions.

However, a 300 mm f/2.8 prime lens will set you back a cool US$ 5, 500, so you may want to have a look at the AF-S 70-200 mm f/2.8, which is just over $2, 000. A somewhat older, second-hand 80 (not 70mm) -200 mm version in good nick can usually be found for less than $ 1, 000, although you'll lose some of the AF-speed compared to the latest version.

Nikon makes a cheap 70-300mm and a good 70-300mm. The good 70-300mm is worth considering. The cheap one is not.

There are no decent lenses, it depends on what you plan on doing.

The 70-300 would be great for sports outside, sometimes even indoors if the ISO performance of your DSLR is good.

Here's a Lens Buying Guide - http://www.smashingcamera.com/lens-buying-guide/