Here are some software that looks at providing some common software required in Windows on the Mac.

AD integration or improvements to the AD integration experience from both a user and administrator perspective

• Admit Mac
• Centrify

Remote control applications

• OSXVNC and some TightVNC compatible clients
• Remote Desktop Connection
• Team Viewer

Chat and Remote Video and Control

• YuuGuu and Skype

AntiVirus

• A good list exist at (http://antivirus.about.com/od/antivirussoftwarereviews/tp/aamacvir.htm)
• Also includes ClamAVX

Firewall Applications

• Flying Buttress
• DoorStop X Firewall
• Firewalk X
• Impasse
• IPNetSentryX
• interGate
• LittleSnitch
• NetBArrier X4
• NoobProof
• Norton Personal Firewall for Macintosh
• sunShield
• WaterRoof
• Firewall Advisor

Network Access Control or VPN

• Impulse
• Checkpoint – (http://www.macnn.com/articles/06/06/26/vpn.1.secureclient.ships/)
• LanDesk Security Suite and Patch Manager