If you find yourself sometimes accidentally hitting the Caps Lock key, this tip will be a God-send. Just open a terminal and type xmodmap -e "clear Lock" to disable it. On my system the keyboard LED for the key still lit when it was hit, but there was no other effect within Ubuntu.
If you work in an office environment or have more than one PC in your home you might be used to connecting to shared folders across the network. Ubuntu's Places > Network view should show the computers that are local to you and let you connect.
Whenever you mistype a password Ubuntu will pause for two seconds before letting you try again. This is for a good reason, because hackers often try brute force techniques to guess the password.
There are essentially two methods used to search for files at the commandline: locate and find. The difference is that locate relies upon a database of files and locations, while find literally searches the file system each time you use it.
If you're sitting in front of somebody else's Ubuntu computer and want to quickly identify which version of Ubuntu it running (not always easy to do from the look and feel if it's heavily customized).
Have you got a vintage camera that won't work under Ubuntu because it's not a removable storage device (which is to say, its contents don't appear in a file browsing window when you attach the camera)?
If you use Ubuntu's Calculator application to work out nothing but trivial financial transactions in dollars and cents (or Euros/cents, pounds/pennies etc), then you can force it to always round its results to two decimal places, depending on which side of half a cent/penny the result is.
When it comes to blocking data emanating from your computer, Firestarter can enact two different modes: whitelist, and blacklist.
Start Synaptic and search for clamtk. Put a check alongside the clamtk entry in the results, and click Mark for Installation in the menu that appears. Agree to install the list of dependencies, that includes ClamAVitself, and then click the APPLY button on the toolbar.
Inbound rules allow you to filter all incoming connections. By default, all uninvited incoming connections are turned away. Creating an inbound rule effectively allows you to create a "hole" in the firewall for certain types of connection to get through, as needed by particular programs.