The wonderful Minolta 100-300 F4.5-5.6 APO Best quality and value tele for your money.
Firstly a bit of background; I am primarily a landscape photog who does a fair bit of hiking and backpacking, so size and weight become important factors for me in my choice of lens.
I don't do a whole lot of wildlife photography unless said wildlife is fairly still. Enter the Minolta 100-300mm APO; which weighs around 1lb and is quite compact, so it's easy to take with me on my hikes.
Now of course small and compact is useless if the quality isn't there, but with this lens, the quality is definitely there and will provide for you stock quality images especially if you stop it down a bit (I find even F6.3 at 300mm does a good job).
This lens goes for in the neighbourhood of 250-300.00 US on Ebay (where I picked up my copy). A definite recommend to those who want a good quality, affordable and lightweight tele lens for stock photography.