Jailbreak Compatibility List
This is a dumbed-down copy of the list that is already created at jailbrea.kr, and I take no responsibility for the credit.

– Check which version of iOS you’re currently on by doing the following on your device:
Settings > General > About > Version

Also, just for reference:
An A4-Device is an iPhone 4, iPod 4th gen, iPad 1st gen, and Apple TV 2nd gen
An A5-Device is an iPhone 4S, iPod 5th gen, iPad 2nd gen & mini, and Apple TV 3rd gen
An A6-Device is an iPhone 5 and 5C, and iPad 3rd gen
An A6X-Device is an iPad 4th gen
An A7-Device is an iPhone 5S, iPad Air and iPad Mini 2nd gen

(iPhone 3g/3gs/4, iPod 1g/2g/3g)
iOS 4.0 – 4.0.2: Use limera1n

(iPhone 2g/3g/3gs/4, iPod 2g/3g, iPad 1g)
iOS 4.1 – 4.2.1: Use greenpois0n RC6.1

(iPhone 3gs/4, iPod 2g/3g, iPad 1g)
iOS 4.2.6 – 4.2.8 or 4.3 – 4.3.3: Use redsn0w v0.9.15b3 (mac/windows)
or open jailbreakme.com through Safari on the device itself!

iOS 4.2.9 – 4.2.10 or 4.3.4 – 4.3.5: n/a

(iPhone 4s) (all other devices tethered)
iOS 5.0: Use redsn0w v0.9.15b3 (mac/windows)

(iPhone 3gs/4, iPod 3g, iPad 1g)
iOS 5.0.1: Use redsn0w v0.9.15b3 (mac/windows)
or for iPhone 4S and iPad 2G, Use Absinthe 0.4 (NOT 2.0.4!)

(iPhone 3gs/4, iPod 2g/3g, iPad 1g) (this is tethered!)
iOS 5.1: Use redsn0w v0.9.15b3 (mac/windows)

(iPhone 3gs/4/4s, iPod 2g/3g/4g, iPad 1g/2g/3g)
iOS 5.1.1: Use Absinthe 2.0.4

(all “current” iDevices)
iOS 6.0 – 6.1.2: Use evasi0n

(iPhone 4)
iOS 6.1.3 – 7.0.4: Use Ragebreak (follow guide (MAC ONLY!!): here)