Even if you don't know a ton of chords on the guitar, you can vastly increase the number of songs you can play by transposing them with a capo. This simple DIY wheel from web site Instructables will help you do it on-the-fly.
While putting a capo on your guitar technically raises the pitch, it also means you can use more familiar chord shapes to play difficult songs. It can be hard to keep track of which shapes correspond to which chords for each capo position, though, especially if you're not a veteran musician. With this simple table (in the form of a wheel), you can easily transpose any song in just a few minutes for easy playing. It doesn't particularly matter what you make the wheel out of or how nice it looks—all you really need is some paper or cardstock and a paper fastener—what matters is the information contained in the table, which the writer of the instructable generously provides for you in PDF form. Hit the link to check it out.
Key Transposing Wheel for Chords [Instructables]