Zoiper - Cross-platform VoIP softphone dialer for SIP and IAX systems
Preme for Windows - Speeds up your window switching.
MicroSIP - MicroSIP is a free portable SIP softphone for Windows based on PJSIP stack.
GridMove - GridMove - A window management tool that can quickly arrange your windows into desktop grids.
Sipnetic - Sipnetic is a free VoIP softphone based on the SIP protocol.
WinDock - WinDock is a window manager ideal for large, or multi-monitor setups. Features: