How are the different online-education websites in terms of being able to take courses at your own pace? I'm interested in trying an online course out to pick up some statistics and machine learning, but I probably wouldn't be able to follow it week-by-week (and not having to wait for a given start date would be great).
All Coursera courses are deadline based. Some of the courses remove their material at the end of the course. Others, such as the database one, are later opened up as self-study but do not offer a certificate of completion.
In the case of edX, MIT's 6.00x course is strictly deadline based. CS50x allows you to take the course at your own pace as long as you finish everything before the 13th of April, 2013.
But those aren't the ones you're looking for. Udacity meets all your requirements. They have open enrollment, meaning you can join in at any time. Furthermore, they have no deadlines. As long as you complete all the problem sets and give the final exam, you get a certificate.
Here are some Udacity courses that might interest you:
Something I found out recently: there are many courses that pull their course material when the course is finished. Even if you are/were enrolled, you lose access. I found this out from the Statistics One course (since you mention statistics), which cut me off in the middle.
Obviously, you can avoid this by downloading all the videos and slides as soon as you have access.
