SkypePTT from Usefulapps is a push to talk client for Skype to be used in conjunction with a Bluetooth enabled PC (the PC links to Skype, the phone is effectively used as a PTT headset). The obvious limitation ishat you need to remain within Bluetooth distance of your PC. Interesting, I’d like to see a client like this for all phones since it basically just makes your Bluetooth phone in to a headset. Link.
Skype for Symbian Based Phones (sorta)