These are from a recent humble bundle that is no longer available for purchase.

Twitch Turbo 1mo - $0.50 (CC required, Expire 2/1/2015)
Reddit Gold 1mo - $0.50 (CC required)
Landmark 1wk Beta Key - $0.80
Trove Beta Key (indefinite) - $1.50

Also, 7-day Xbox Live Code (region-free, no expiration) - $0.30