Yep Model Glue. The liquid kind works best. I prefer Tamiya extra thin, Gunze Mr. Cement, Ambroid Proweld, or Tenax-7R (the best). Hold the pieces together and brush on at the joint. Capilary action pulls the glue into the joint and fuzes the pieces together. Fuzed pieces are more resiliant than pieces glues with CA, as CA joints do not have much torsional strength (hard to pull apart, but easy to twist/bend apart). Because of this, joints made with liquid cement are mor flexable than any other joint I have found, but are strong enough that on polystyrene thinner than .025", you are more likely to tear one of the pieces than pull them apart. Liquid cement leaves cleaner joints than the Gel that comes in the old Orange tubes we used as kids, and creates a better bond.
Hope this helps.
EDIT: oh, and most of these work on ABS too. Very helpful in joing ABS to PS.