I just bought a cheep OBD2 code reader, really nothing fancy, it was only $20.
If you're looking for codes here is the site. http://www.obd-codes.com/
Please note that the most common codes that ppl are looking for are the 'P' codes, there is a link to the 'Full List' at the bottom of the first column.
After clicking on that link you can either click on the manufacturers logo to get specific codes for that maker or go down to directly under the logos for links to the 'B' or 'C' code the links if that's what you want.
Just go in and look around.