I have the Sigma 70-300mm f/4-5.6 APO Zoom Macro Super II lens. For the money I think it is a good quality lens.I bought my lens at B&H.
Check these two sites.
I personally think this is a very good lens for the money and it is within your budget.
I took this photo with this same lens.
That was also taken with a D70.
For action and low light stuff you really need a 2.8 lens, and they start around $800.00 for Sigma. For the image stabilized lenses they are quite a bit more.(I wish I could afford one.)