Online workshops and writing critique groups can be an invaluable resource. Some workshops are static, in that you read the instructions and do the work privately without any interactive instruction or critique. This site posts assignments and exercises from their real life workshops.
Most groups have a mix of published and unpublished writers.
In many cases, participants must have e-mail, and the web site is really just an instruction area to explain how to join the group. In other cases, all work happens on the web site. Most require that you critique others as well as submitting your own work.