Some of the sites listed come from universities and concern ongoing projects, particularly about historical corpora and are definitely worth visiting. The links have been checked at the time of the most recent update (see introduction in left-most menu for latest date stamp). Hopefully, the sites still exist and have the same address as when they were first recorded.
Another domain which may be of interest is that of digital libraries. The best one is probably the Eletronic Library at the University of Virginia (last node on tree on left) which is highly recommendable.
Generally, sites such as those on the left, e.g. that from the University of Toronto, contain links to further sites with more information on the history of English. Students can use such sites as springboards to find more precise information, especially when doing work on a particular aspect of the subject.