As for strings, I personally like:
http://www.amazon.com/Elixir-Nanoweb-Bronze-Acoustic-Strings/dp/B0002E1O2C/ref=sr_1_2?ie=UTF8&s=musical-instruments&qid=1281109725&sr=8-2
They are a tad more spendy than average but its definitely worth it. Assuming your a beginner you want to start with light strings, it makes things a little easier. I have been playing for years now, and I still struggle with a heavy gauge for acoustic honestly...
As for nylon strings, I dont know enough to point you in a certain direction. Others are going to have to chime in on that...