Selling for 3-4 keys:

http://backpack.tf/classifieds/search/738/1/0 - One selling for 4 keys, rest have been unsold for a while

http://www.tf2outpost.com/trade/10354677 - Selling for 3 keys

http://www.tf2outpost.com/trade/10284941 - Selling for 3 keys

http://www.tf2outpost.com/trade/10359407 - Painted selling for 4 keys

http://www.tf2outpost.com/trade/10361788 - Selling for 3 keys

http://www.tf2outpost.com/trade/10357349 - 4 keys, painted

Unsold at current price (24 hours or older):

http://www.tf2outpost.com/trade/10204438 - Unsold for one week

http://www.tf2outpost.com/trade/10330649 - Unsold for a day at 4 keys

http://www.tf2outpost.com/trade/9700745 - Backpack.tf price, unsold for 3 weeks

http://www.tf2outpost.com/trade/9974703 - Unsold for 4 keys, 2 weeks

Sold:

http://www.tf2outpost.com/trade/10268359 - Sold for a S.F worth 4 keys