"These include" or "This includes"

As Sam said in his comment, the crux is what precedes the "this/these include(s)", not what follows. As a matter of fact, "This includes administrators and normal users" can be just fine, depending on the context.

That said, these can still be a little tricky. For example:

Several different users can change their own passwords; these include administrators, and normal users.

The "these include" refers to "several different users." But:

No users are allowed to change their own passwords; this includes administrators, and normal users.

In this case, the "this includes" is singular, because it refers to the single principle that no user is allowed to change a password.

Corruption was uncovered at many levels across the organization; these include both administrators, and normal users.

Here, "these include" refers back to the many levels where corruption was found.

However, instead of trying to figure out the correct usage, a better option would be to use the more all-encompassing including. In fact, this change seems to improve the sentences:

Several different users can change their own passwords, including administrators and normal users.

No users are allowed to change their own passwords; including both administrators and normal users.

Corruption was uncovered at many levels across the organization, including administrators and normal users.

Get rid of this this, and this problem goes away.

A footnote (to underscore how tricky the this/these choice can be): I could have said, "In fact, these changes seem to improve the sentences..."

Which is correct? If I am referring to the single hint of replacing the phrase "this includes" with the word including, then "this change seems to improve" is appropriate. But, if I'm referring to the three individual improvements found in each example, then "these changes" would be better.