I had a set where there were square (2" sides) and triangular frames that fit together tongue and groove, with connectors for corners, along with various things that would snap into the frames (skylights, clear and opaque window and wall materials, etc.) This was great for crating various archtectural designs. I cannot recall who made it or what it was called.

Can anyone direct me as to what this may have been sold as?

Possibly a Super City set?
Super City is made of plastic frames which connect at the edges with grooves and studs into which fit a variety of wall panels. Frames can be connected at right angles by grooved and flanged columns. Frames are primarily square with some rectangles (half squares) and triangles (diagonally halved rectangles). The inserts are mostly wall finishes in either thin textured and coloured opaque plastic or windows in coloured (and sometimes textured) transparent plastic.
http://en.wikipedia.org/wiki/Super_City_(toy)
(good links on the bottom of the Wiki page... )

Hmm, tried to edit my above post, can't seem to do it... the link I provided was missing a parenthesis. (just tried to include it here, same thing, weird..) When you go to that link click on 'did you mean Super City (toy)' ....