ReDJ is a nice little extension that is excellent for creating 301-redirects, it is basically what it is made for. Functionality is similar to the Redirect Manager in the Joomla core, but it works better. It can be used for simple 301-redirects, and it also contains a logging functionality for 404 errors, so that they can easily be rerouted to the correct ones.

What makes it stand out from the Core Component is the possibility to use macro's.

It can easily be used for rerouting non-SEF URL's to the SEF ones:

Bear in mind that questionmarks need to be escaped with a backward-slash, as in this example.

The extension comes in a free and in a commercial version, but the free version already offers excellent functionality.