I got a Simple Mobile Sim today and am paid up for one month of "unlimited" phone, text and Net. I was startled at how fast I got set up (I was using Tmobile before). It took less than five minutes. The APN is the word "simple" without quotes. $40 a month.

The Sim is something like $12 if you buy it from them or 1 cent + shipping if you buy it on eBay. (They also sell microSims if you have an N9.)

I have simple needs and usually use WiFi, but it's nice to have my N900 with more options. Simple Mobile works perfectly for me.