There is only one B707-120B still in active service, a B707-123B(F) still flying around somewhere in Africa as 3D-ADK (Swaziland rego). It was originally American's N7585A (1967). It was spotted in Johannesburg, South Africa earlier this year.
There are also three B707-138Bs still flying, one of which is John Travolta's personal aircraft ... it's just been repainted with blue stripes and is now Stage 3-compliant. Remember, though, that the -138 was a shorter version of the -120 and it was only bought by Qantas of Australia (13 aircraft). At least another three of these aircraft are still extant in storage.
There are also five B720s still in operation, three of which serve as engine testbeds. The B720 fuselage length falls inbetween that of the B707-120 and the B707-138.