I want to cut acrylic sheet, and I was wondering if there is a special end mill for doing this so the edges of the plastic stay smooth and dont need to be polished after the cut.

Onsrud makes bits for plastics. http://www.onsrud.com/index.html
Vortex also has some. http://www.vortextool.com

If you want a polished edge, you'll probably have to polich it, but it is possible to get a very smooth edge. The above tooling is generally for routers, btw.

slot drill...

WHat spindles speed / material thicknees / cutter diameter.

Machine ridgidity will have a marked effect of the surface appearance as well. You can see what you cant feel.

2 flute straight cutters 3/8 or 1/2" I have had excelent results at 15-20 k spindle speeds, air blast and 100-200 ipm feeds. So acrylics are harder or softer which will also affect the cut IE cast / extruded sheet.

To get a perfect edge a diamond cutter will works best, and a diamond edger will give you the best machined finish.

Hope that helps.

Depending on the application, I have used router bits and Dremel bits. The Dremel bits work well in a variety of materials and they are inexpensive.

Most plastics manufactures recomend using router type cutters.