Here is a blues riff:

Blues Riff WAV File

Note: The above sound file was created by WeGotRecords, on a Real Live Guitar!

Blues Guitar TAB Books:

The New Essential Blues Guitar: Authentic Guitar-Tab Edition (The New Essential Guitar Series)

Not too many songs, but a few good ones are by BB King and Jimi Hendrix.

Boogie Blues Riffs : 25 Classic Patterns Arranged for Guitar

Comes with a CD that has 25 'essential blues riffs'. For beginners

See Also:

Punk Guitar Tabs

Rockabilly Guitar Tabs