Shimo is a felexible VPN client that supports most protocols including Cisco VPN connections.
Shimo started in 2006 as a replacement for the ugly and rather limited graphical user interface that came with Cisco's VPN client. However, since then, Cisco's VPN client is now supported naively in OS X 10.6 although it is still very limited in controls and preferences. Shimo however, gives you much more control.
Using Shimo is easy. Once installed, it may ask you for your system password so that you can update Shimo's drivers to support as many VPN protocols as possible. To setup a new connection, just click on Profiles and then the "+" symbol to add a new connection. You can choose to either import a profile or add the details manually yourself. In the case of Cisco connections, this usually requires the server address, username, password, group name and group name password or "shared secret".
There are many customizations and preferences beyond this although for most people, they won't need touching. However, I found myself trying to change some of them in order to make Shimo connect to a Cisco VPN. Using Snow Leopard, I could only ever get as far as "Securing" in the connection status dialog. Whether this is because my settings weren't quite right or whether its because Shimo simply doesn't support Cisco very well in Snow Leopard I'm not sure.
Note that in this free version, your connection times will be limited and you will be subject to a nag screen asking you to upgrade from time-to-time.
Overall, Shimo is a slick and highly flexible VPN client but you may have troubles getting it to work with Cisco VPN connections.
