Jamey Heary over at Network World compiles five little-known but useful features of the Cisco ASA firewall.  He gives examples of configuring application firewalling, embedded host posture assessment and remediation for VPN clients, authentication and authorization for your ASA Admin users directly via LDAP, allowing TCP applications over clientless sslvpn without plugins, and controling clientless sslvpn user access via URL access lists.