Just checked the latest amazon deals and I found that one: 10% discount on Sigma lenses when you buy a Sony.
Some Sigma lenses are really good and I suggest you to read the Sigma reviews from photozone!
The original amazon deals-text says:
“Capture an Extra 10% Savings on Select Sigma Lenses
For a limited time, save an additional 10% on select Sigma lenses with combined purchase of a qualifying Sony digital SLR from Amazon.com. Simply add a qualifying DSLR and qualifying Sigma lens to your Shopping Cart, and we’ll automatically apply an extra 10% discount to the price of the lens at checkout.
Offer valid through December 18, 2009. Applies only to purchases of products sold by Amazon.com, and does not apply to products sold by third-party merchants and other sellers through the Amazon.com site.“