Cobdump3 is a handy software for those who use Caligari TrueSpace to make objects and avatars. It converts a .cob file to a .rwx. Even though the Active Worlds' browser works with .cob files, most ppls insist on .rwx. The problem with cobdump3 is that you have to type manually the exact location of the .cob file. However, it's free and it works.
I've used a lot of software for zipping files, and I find Multizip to be one of the easiest to use. You can even password protect a zip file with it. It's only downfall is that it can't unzip.
Animcart is a great software for making animation textures like fires and waterfalls. I use it all the time. I highly recommend it for any serious world builder. And even if you don't own a world, you can still use these animation textures anywhere in Active Worlds with a URL link.