For those of you creating texture packs, here's some notes on how to optimize your packs before release:

1) If you are using PNGs, dither all your images down to custom 8-bit (256 colour) palettes -- these are more than adequate for most textures and are often up to 4 times smaller than their 24-bit counterpart.

2) You don't need to use 24-bit PNGs at all unless you want special effects for transparency. In actual fact, in these cases you'll be making a 32-bit PNG (24-bit + 8-bit alpha).

3) Compress all your images using PNGOUT or PNGCRUSH -- these are command line tools that can significantly reduce your file sizes, especially if you've been using Photoshop as it's PNG compression sucks.

4) Delete all extraneous files from your folders before you make your ZIP file. These include:

thumbs.db - a windows generated cache of all the thumbnails in your folders, if you've been using thumbnail views. These can get very large! Depending on your system settings, they may be hidden. Use Windows Explorer to set your hidden files to visible -- then you can delete these caches. A quicker way to do this is in DOS: open a folder at the root of your textures folders and type the following:

attrib -R -H -S /s *.db
del /s *.db

*.jbf - Cache files generated by Paint Shop Pro

desktop.ini - Windows settings files for custom folder thumbnails, etc.

You may have any of the above files in any of your folders, so you'll need to check each carefully.

I'm at work right now, but will add to this thread when I think of more stuff from home.