I think the new GitHub stickers are from http://www.clubcardprinting.com/

They're located in the Castro in San Francisco and the staff is super friendly and the stickers are affordable and have a very quick turnaround. I've used them for stickers for a side project and they had them done in a day.

My friend from Scribd recommended them, so if you go with them, it's nice to mention Scribd as a referral.