For straight cuts on thin acrylic, the hot ticket it to score it using a straight edge and a razor knife, then bend it along the score line over the edge of a table, and SNAP! You get a nice clean cut if your score was clean.
When doing glass or plastic, NEVER re-score the line. You get one shot to drag the blade through, you need to go fast, with a lot of pressure, and never go back over the score line, or you end up getting a jagged break line.
For making curved cuts and things, put a 1/8" pin cutter in a router table, and slide the sheet through it.
If you gotta make tons of straight cuts, a "tripple-chip" carbide table saw blade does a good job.