I found a nice trick that allows you to UZ3 compress maps very easily... just right click on a .ut3, .upk, or .u file in Windows Explorer and select "compress" in the context menu.

UZ3 compression is a way to download maps and mods from a redirect quicker... think of it as UT3's built-in zip format. Normally, you have to use the command-line to compress packages with UT3.

This trick adds data to your registry that Windows Explorer uses to create the context menus when you right-click on a file. I can't take full credit here. I started with the information posted here.

Installation

1. If you have the boxed version of UT3, download this .reg file. If you have the Steam version of UT3, download this .reg file.
2. Double click the .reg file and click allow/ok as many time as you need to. You will finally end up with some data added to your registry.

Usage

1. Using Windows Explorer, find a .ut3, .upk, or .u file that you want to compress, right click it, and select "compress" from the context menu.
2. Wait for UT3 to compress the file and close the terminal window when it is done.

Screenshots

Caveats:

1. You can only compress one file at a time using this method. I have found that UT3 tends to choke when you try to do a bunch of files at the same time.
2. If you try to compress a file that is in your "Published\CookedPC\CustomMaps" directory, UT3 tries to put the uz3 in your unpublished directory but it fails to do it correctly and you end up with a new Unpublished directory under Published. It is best to copy the file(s) from CustomMaps, probably just to your root Documents folder, then compress.