Yes there is. its called scriptographer. its a free illustrator plugin that creates halftones in whatever size shape you want.
If you are looking to print halftones for color separation, then your best bet is to go with the RIP or print to a post script printer. but if you're looking for a halftone effect that you have a bunch of control over and has a unique look, go with scriptographer.
You can download it for free here...
Scriptographer.org - Download
There is an easy tutorial to follow under the 2nd explanation.
http://www.bittbox.com/illustrator/b...-raster-images
Its worth it! good luck.