We offer unlimited cpu and unlimited memory for the most part. The way it works is as long as you're not causing anyone else's website to load slowly or go offline you're fine. Keep an eye on this image
If that number goes over 20 and your account is causing the most load then you might get suspended. There are two types of high load suspensions: spike load, and sustained load. Sustained load is like if you have a blog that gets really popular and you're getting like a million hits per day. Spike load is stuff like web proxies such as glype or file transfer scripts like rapidleech. These scripts can cause load to spike really high when used even if it's only one person that is accessing it.
I recommend checking in occasionally to see your load levels if you're curious. Just make a post and we can tell you how you compare to everyone else.