Mark said:

"You can take the F#7 chord that Rick mentioned ("Take a standard "D" chord...but..play it on the 2nd, 3rd, and 4th strings....") but use your second, third and fourth fingers to make it. This will leave your index finger free to add the F# on the bass E string. The A string is damped out by touching it with the index finger. This gives you a great sliding or movable 7th chord."

I like that chord too - actually Willie-O showed it to me - but the only problem is that the high E string isn't accounted for, so it isn't fully movable. But if you finger it like this, it is:

Thumb on 6th string at second fret, and dampening 5th string.
Index barring strings 1, 2, 3, and 4 at second fret.
Another finger (your choice) on 3rd string, third fret.

(an F#7 in this example - the tonic is on the 6th string.)

Another movable 6-string dominant 7th shape is a variation on the Bb6 described in the opening post of this thread.

The tonic is on the fifth string, so for a B7 the spelling would be:

Thumb on 5th and 6th string, second fret.
Ring finger barring strings 1, 2, 3, and 4 on the fourth fret (try pressing down the middle finger right behind it to make it easier).
Pinkie on 1st string, 5th fret.

Marion

PS It's ironic - we're talking about chords that can be slid around sideways, but if you learn enough of them, then you can play all the chords of a song in any position without moving your hands sideways at all...