One great resource for mathematics/statistics and varriety of other topics is academicearth.org which features the lectures from Universities such as Harvard, MIT, Yale, Stanford,... For statistics, there are six classes listed. Unfortunately, there is no topic specifically to the biostatistics. Another resource is open course which currently listed 500 free online courses from top universities.
For biostatistics, while there is no video lectures, there are recorded lectures in mp3 format. For example, there are five biostatistics classes listed at education-portal.com.
- Introduction to Biostatistics
- Methods in Biostatistics I
- Methods in Biostatistics II
- Biostatistics Lecture Series
- Biostatistics for Medical Product Regulation