I've published a few gems, mostly to scratch some itches. They're very much works in progress.

• Kentouzu: Adds drafts to ActiveRecord models. Think paper_trail, but forward instead of backward.
• Rate Limiter: A gem that limits the rate at which ActiveRecord model instances can be created.
• RStat: A very simple gem that extends some of the core Ruby classes (mostly Array) to give them statistical methods.
• Safety Check: Selectively add type safety to your methods.