The Khan Academy is a great resource for learning maths and science. There are a few tricks when you start using the site and here are the things I've discovered over the last couple of weeks using the site with my daughter.
Step 1 (Optional)
Watch this talk by Sal on his vision for the site.
Step 2: Watch this overview that shows the range of topics available
Step 3: Using either a Facebook or Google account log into Khan Academy
Step 4: Select the Exercise Dashboard from the top menu. This is a lot less confusing than trying to scroll through the video library. The dashboard also suggest further modules to study.
Step 5: Pick a topic from the list -- this takes you to the drill exercises, which you can start straight away or look at the accompanying video. Remember that you can rewind and replay the video as you need to make sure you understand. You can also pause the video and attempt the example questions that Sal uses before he demonstrates the answer if you feel confident enough.
The Knowledge Map shows you where you are and shows you were you are going.
I'll update this post if I discover more newbie wrinkles.