Flip4Mac
If you are on Mavericks (MacOS 10.9), you MUST pay for the "Player Pro" version of Flip4Mac to remove the audio watermark (cuz version 2 won't work on Mavericks). If you are not on Mavericks yet, then please read on.
Do NOT get the latest version of Flip4Mac!
Starting with Version 3, they have introduced audio watermarking so that you now hear "This is a demonstration of Flip4Mac" every few minutes! Very annoying!
Fortunately, you can download the Latest Version 2.4.4.2, which has no audio watermark.
If you have already installed Version 3, please Uninstall it first, then run kJams and go to Preferences->Audio and click "Clear Cache", then quit kJams.
After you install Version 2, go to System Preferences->Flip4Mac->Update, and set "Check For Updates" to "Never".