You can use the above site to gauge your strength.
When you get to the point where you are feeling good and getting close to your exam date (i.e. within a week), you can use this site for 3 days of free practice tests (one of the better ones from what I understand).
You can do a couple of these – one on Friday and one on Saturday (and then no more practice tests :-). These guys also have unlimited access for a fairly hefty fee ($100 US).
These are others that most aspirants use as well – tougher, so do them earlier to figure out your gaps. One is 75 questions (online), the other is a PDF (175 questions).
The above site has some benchmarks, but you can also find this type of information by searching the internet for practice test benchmarks. He also has some good study notes, and formula pages etc.