these are great They are available in all 4 subject areas, and are pretty stress-free. They just take 10 minutes so you can easily do one every day without a huge commitment. There are 20-30 in each book, so over a 3-4 month period you could easily work through them all.
You can use them to idenitfy isolate any problem areas and work on them, before moving on to the full-sized tests themselves.
I came across them in WHS at the weekend, and they seem ideal as a 'little extra'.