I have a great condition Sigma AF 70-200mm f/2.8 EX DG HSM APO (Canon mount) for sale. Lens has no marks, worked very well for me, but I upgraded.
$600 obo. Comes with lens, hood, carrying pouch, aftermarket lens cap.
Here is a review http://www.photozone.de/reviews/324-sigma-af-70-200mm-f28-ex-apo-hsm-dg-lab-test-report--review.