TinyWall is a free software to harden and control the advanced firewall built into Windows Vista and Windows 7.

Features:

Non-intrusive operation
TinyWall lets you work while protecting you. No annoying popups and simple configuration.

Lightweight
Using the advanced Windows Firewall built into newer Windows versions, TinyWall´s performance impact is neglible.

More than just a controller
Password lock, firewall tinkering protection and built-in tight firewall rules make TinyWall secure.

Safe operation
No drivers or kernel-components are installed, which keeps your system stable.

Convenient
Firewall modes and lots of other convenience features make TinyWall extremely easy to use for anybody.

No cost
100% free, no ads, no artifical limitations, no upgrades.

Editor's Note: After installation TinyWall blocks all communications. To use the internet or network-enabled applications, select one of the "Whitelist by ..." options in the tray menu to unblock specific programs.

Limitations: Vista users need the latest Microsoft .Net Framework.