There are quite a few variations on the blues, often people will play the I chord for the first 4 bars skipping the IV chord in the second bar. Here are a few popular versions of the blues.
1. Boogie Woogie
www.en.wikipedia.org/wiki/Boogie-woogie
2. Sweet Home Chicago by Robert Johnson (in F)
Sweet Home Chicago ala Blues Brothers (in E)
3. Everyday I Have the Blues by Pinetop Sparks
http://en.wikipedia.org/wiki/Every_Day_I_Have_the_Blues
Lyrics http://www.azlyrics.com/lyrics/bbking/everydayihavetheblues.html
Everyday I Have The Blues ala John Mayer
Everyday I Have The Blues ala BB King
Everyday I Have The Blues ala Count Basie Orchestra
Everyday I Have The Blues ala Eric Clapton
4. What’d I Say by Ray Charles (in E)
5. Johnny B. Goode by Chuck Berry (in Bb)
Johnny B. Goode ala Michael J. Fox
6. Killing Floor by Hollin’ Wolf (Blues in A)
Killing Floor ala Hendrix
7. I Feel Good by James Brown
8. Pride and Joy by Stevie Ray Vaughan
9. Rock N’ Roll by Led Zeppelin
10.Batman TV show Theme Song
11. Spiderman Cartoon Theme (in Cmin)
Lyrics http://www.lyricsondemand.com/tvthemes/spidermanlyrics.html