Aside of being a (pretty bad) mail client, Lous Notes is quite a powerful non-relational database platform. You can see some examples in the other posts in the Lotus Notes category. Here is a hack that shows a bit of hidden power in the ln 6/7 client.
You can use the (quite bad) internal web-browser to access some functionality of the host system. This can be particularly useful in a locked-down environment (ex. Citrix).
Many people in a IT-Support environment will recognise this situation. You need to access the command prompt, but cannot, since it is not available through the Citrix published apps or desktop.
Here’s a way you can work-around this by using the Lotus Notes Client:
In the Lotus Notes Client, check if Lotus Notes is set as the Default Internet Browser. If this is not so, it will most probably open the links in the Microsoft Internet Exporer Window, which is limitred by the system limitations.
You can access this setting in the Location Settings (File ->Preferences -> Location preferences)
Once done, you need to check that the Address bar is present in the Client Top toolbar.
To access the Windows command prompt, open the following link in the address bar:
file://c:/windows/system32/cmd.exe(somehow I could not make it work using the environment variable like %system% so you’d have to know where your windows folder is located)
From there, you are free to go 
Have Fun!