Below are some online articles for revision in biostatistics. Click the titles and you'll be directed to the respective sites:
All the Biostatistics notes you will need for a quick revision
Quantitative Methods for Scientific Research (How to Choose a Stat Test and How to Interprete the Results)
Epidemiology-Biostatistics Board Review
Common Statistical Tests (Lecture Notes, PDF)
Descriptive Epidemiology and Descriptive Statistics
Generally, I think the following websites are helpful for online revision:
If you have other websites to recommend, please do so. Have fun revising.