I recently got some "fettuccini" yarn on sale form Lion Brand. It's kind of like T-shirt yarn. I ended up creating a shoulder bag out of almost an entire skein. The yarn is thick so I think the purse ended up feeling kind of heavy.
It's basically 16 stitches knit in stockinnette till I like the size (when folded in half). Then I decreased from the edges (and occassionally the middle) to make a triangle for folding over.
Once that was complete, I switched from 15mm needles to 10 mm needles and knit while casting off along one of the tapered edges (you could crochet it because to knit, you have to pick up stitches). Then I folded the purse in half and knit one side together with the inside facing out. I then knit loosely along the bottom so I could knit the other side together. Then I added two stitches and knit an icord for the strap. Then I attached that and knit/cast off along the other side of the tapered edge back to the point. Then cut, tie and hide the ends. Finally, I sewed on a large button.