One of the next things on my to-do list was to research the best tools for SQL CE. I think the best bet at the moment is WebMatrix, although it is much more than just a SQL editor.

Edit - I should also add that SQL Server Compact Toolbox has a version that is a tiny, no-install exe that offers some management ability, but its lack of an editable grid to make changes is a major drawback (updates have to be done by constructing SQL statements).

The market is missing a simple SQL CE editor like we had with SQLite. I expect that some will appear as SQL CE grows in popularity. It's a good opportunity for a new open source project.

BTW, if you have Visual Studio 2010 SP1, you can also use that.