Steam Screenshots feature (now in beta)
If you go to your Steam settings and opt-in to the beta, you’ll get access to the Steam Screenshots feature. Hitting Shift+Insert (depending on keyboard shortcuts in Steam) in any game (even non-Steam games as long as the Overlay works) will take a screenshot, which will automatically upload to SteamCloud when you quit. Once there, you can publish the shots to your profile. Pretty spiffy. The beta also shows off the improved voice codec, which improves the sampling rate of voicechat without a major bandwidth hit.