I've been checking out skype as an alternative to ventrilo because we were getting some really bad feedback, but I was really surprised to find there was no real PTT support other than a mute mic hotkey.
So I decided to make a little utility program for skype.
(Skype PTT in action, nevermind the not responding :P)
1. Start Skype as normally and login.
2. Download and unzip from the link below, if you're having trouble starting the program you should download and install the .net 2.0 framework or higher.
3. You may get a screen saying SkypePTT.exe wants to use Skype, click Allow access.
4. Call and press your hotkey to talk! (note u may have to click abit before talking because of the mute/unmute delay).
This version is outdated, get the new version here: Skype PTT 1.0 Final.
If u still want to get the old version for any reason click here to download it.
Note: Requires Windows XP or higher and the .net 2.0 framework at least to run.
Personally tested in Windows XP and Vista 64 bit.
Update: If it's failing to run try registering the skype dll file.
Click on Start
Type in cmd in Run
Then cd to the folder where the files are extracted ->
Type in: regsvr32 Skype4COM.dll