Love it or hate it, there's no denying how popular the service is. There are now Instagram users, and apparently Facebook could see its worth, considering it's working to purchase the company for $1 billion. Instagram isn't the only photo filter app out there, though, and there are definitely geekier options. Here are five of them for your enjoyment and amusement.

Forget computer-generated filters--is the real thing. InstaCRT actually displays your image to a CRT screen, snaps a photo of it, then sends the resulting photo back to you. The process takes only a few seconds, and it leaves you with a genuine retro CRT effect.

InstaCRT "Sorry Instagram, but this one genuine filter totally one-ups your filter selection.

The app is only available on iOS for now, and it'll set you back $2.