On the ASA, you can enter "show vpn-sessiondb" command, it shows such info.

demo-asa# sh vpn-sessiondb

Active Session Summary

Sessions:

                           Active : Cumulative : Peak Concurrent : Inactive

  SSL VPN               :       0 :        145 :               7

    Clientless only     :       0 :         30 :               2

    With client         :       0 :        115 :               3 :        0

  Email Proxy           :       0 :          0 :               0

  IPsec LAN-to-LAN      :       0 :          0 :               0

  IPsec Remote Access   :       0 :          0 :               0

  VPN Load Balancing    :       0 :          0 :               0

  Totals                :       0 :        145

License Information:

  IPsec   :    750    Configured :    750    Active :      0    Load :   0%

  SSL VPN :     50    Configured :     50    Active :      0    Load :   0%

                            Active : Cumulative : Peak Concurrent

  IPsec               :          0 :          0 :               0

  SSL VPN             :          0 :        145 :               7

    AnyConnect Mobile :         61 :         61 :              61

    Linksys Phone     :          0 :          0 :               0

  Totals              :          0 :        145

I am sure there are much better alternatives such as Cisco ACS which are production quality.

But, I recently installed Microsoft IAS on my Windows 2003 server and then configured Accounting for my VPN group policy. Then I used a free software "IAS log viewer" which is able to provide the usage of my VPN.

See the article below for Microsoft IAS configuration on Win2k3:

http://www.cisco.com/en/US/products/hw/vpndevc/ps2284/products_configuration_example09186a0080094700.shtml

The entire procedure took me less than an hour. The IAS log viewer generated nice reports as well.

Thanks,

Kiran