Amazon have a 'PC Download Labour Day Deals' event starting now with 2K games and bundles.
Some are Steam redeemable some require Origin and others are via the Amazon download service.
A great bargain I feel is http://www.amazon.com/Desert-to-Sea-Bundle-Download/dp/B0091… "Desert to Sea Bundle" which is Bioshock 1 and 2 (non-steam) and Spec Ops the Line (steam) for $19.99 USD (cheaper than Spec Ops by itself).
Also Darkness II (I dont think it is steam, but feel free to correct me) is only $9.99 USD. Great game at a great price.
UPDATE
lots more titles added now
http://www.amazon.com/gp/feature.html/ref=amb_link_365019362…
Does amazon have their own steam-like DRM service?