AirMagnet's Laptop Analyzer

Similar to their popular Handheld Analyzer, AirMagnet's newly-released Laptop Analyzer offers functions such as WLAN administration, installation surveying, security assessment, connection troubleshooting, performance management, and operational support -- all from your notebook (as the product's name implies). This Laptop version, however, has some enhancements worth noting, such as larger screens, new alarms, larger buffer, printing, and better import/export capability.

The entire package includes software and a Cisco Aironet AIR-PCM352 802.11b PC Card with a fixed omni-directional antenna. In order to support higher gain antennas for directional link testing and rogue access point hunting, you need AirMagnet's Laptop Pro ($3,795). A combo version is also available that includes both the Handheld and Laptop software ($4,495). 

Pros:

Intuitive screen layout and excellent usability. 
Rich security auditing features 
Comprehensive protocol capturing and analysis functions. 
Cons:

Limited RF spectrum analysis. 
No support for 802.11a.