Your going to want to use a product called weld-on. I personally like the weld-on #16. It comes in a couple of different numbers. I just like the 16 because its more of a "thicker" consistency and easier to use and work with IMO! I know you can get it at Midland Plastics here in Green Bay. If you have a specialty Acrylic shop around you thats your best bet. Last time I checked I know Menards and Home Depot don't sell it.
I have never really cut acrylic except for Holes for bulkheads. I think the #16 I have used is nice and easy to use. Kind of reminds me of using the glue that one used as a kid building the car models. If that makes sense or helps.
What are you cutting? Holes? Cutting to size? I used a really high tooth-count blade on my table saw to cut the plexi to size for my sump. I just used a regular hole saw for the holes for my bulkheads. (drill slowly...if I remember right - and then when you're almost through, flip it and drill from the other side)
The thicker the plexi, the less likely you will be for it to chip. But I just recently cut some REALLY thin stuff on a table saw with a blade made for cutting it, so even the thin stuff can be cut nicely if you have the right blade.
If you have a cut list and haven't bought it yet, take your cut list with you to wherever you buy it and they should be able to cut it for you. I know Lowe's can - not sure about HD or Menards. And of course glass shops can too.
If you're cutting for a sump, keep in mind that the stuff swells over time - so be sure to cut a bit small or you will crack your sump.
I second the above mentioned saw, and you also need to carefully sand/polish the edges where they butt together, the glue is very thin and will not fill gaps very well at all.