It's a nice little web widget (for the sake of argument let's just call it that) that will tell you if your iDevice is jailbreakable and what method/program will work to complete the desired task.
JailbreakStats was created for that simple purpose of letting you know if you can jailbreak your gadgets. You can check it out here. First you select the firmware of your iDevice, which can be found in your Settings app under General, then tap on About and scroll down to the Version number. After that, you select your iDevice and click on Check Status. A little popup window will show up giving you some simple information that I'm sure will be helpful.
Follow me on Twitter and/or Google+ and make sure to come back often for new posts from me; I have something planned out for the weekend and I hope it'll be as exciting and informative as it was for me. Don't forget to like and share my blog with your fellow iDevice friends! I really appreciate it!
UPDATE: Forgot to mention this old guide I had in my bookmarks called Jailbreak Wizard. This is the original site I used for quick look up to figure out if an iDevice could be jailbroken. Select your iDevice, select the model, what iOS is running on it (again, it's under Settings->General->About) which would be the Version number, BaseBand is the very last number in the About section, and finally select the operating system of the computer you're using. Click on Check your iDevice and there you go! Simple rundown of the information you're looking for.