Simple chord progressions that are fun to jam on are always welcome. I like to jam on minor seven progressions because of the mood they create and the kinds of melody lines they conjure up. Here's a progression that's similar to the song "Long Train Runnin'" by the Doobie Brothers. Play it like a variation on a blues progression. Start with four bars of an Em7 with your first finger making a bar across the 7th fret, your middle finger on the B string 8th fret and your ring finger on the D string 9th fret. Then play two bars of Am7 at the 5th fret with your ring finger barring the D, G and B string and your middle finger on the low E string. The A and high E strings are dead. It's a classic Mel Bay chord voicing. Now go back to another two bars of the Em7. The turnaround is one bar each of C7 and Am7 and two bars of Em7. The C7 chord is played with a first finger bar on the 8th fret, your middle finger on the G string 9th fret and your ring finger on the A string 10th fret.
Let's do a riff that goes with this progression. The first phrase starts with two hammer-ons. Go from the 9th to 12th fret on the D string and repeat that hammer-on in the same frets on the G string, but add a pull-off back to the 9th fret. The last three notes of the phrase are played by your pinky on the 12th fret D string, followed by your first finger on the 9th fret D string and then on the 9th fret G string. What you've done here is an elaborate way of playing the note E. For the next phrase, place your pinky on the 12th fret B string and pull-off to the 10th fret. Now set your pinky on the 12th fret G string, followed by the middle finger on the 10th fret B string. Now go from the 12th to 9th fret on the G string, followed by the 12th fret on the D string. Now do two pull-offs, 9th to 12th fret on the G and then the D string. The phrase ends with the E note on the 9th fret G string followed by the G note on the 10th fret A string.
For the Am7 chord, play the first seven notes of the phrase just described and end with the pinky on the 12th fret G string, followed by the middle finger on the 10th fret D string.
When you're back to the Em7 chord again play the seven opening notes, then play the 11th fret G string and bend it up a half step and back, pulling off to the 9th fret. Do a pull-off from the 12th to the 9th fret on the D string and end on the 9th fret G string.
For the C7 chord, we've got a new riff. Begin on the 12th fret B string, followed by the 9th fret on the G, 10th fret on the D, a 9th to 12th hammer on the G string and a 12th to 10th fret sequence on the B string.
End the progression with the Em7 chord, and play this riff twice; hammer from the 9th to 12th on the D string and pull 12th to 9th on the G.