Most Linux systems have native support for the major archive types. But in order to get .7z files to work in Ubuntu Hardy Heron do the following:
System -> Administration -> Synaptic Package Manage
Search for p7zip and install
Now they should work just fine.
One of the hurdles I needed to tackle in my move to Linux was making my ssh keys work. It took a little digging but eventually I figured out the process.
Download puttygen.exe for windows. Open up your ssh keys with puttygen and choose export. Export them as OpenSSH keys.
Copy these keys over to linux and put them in ~/.ssh
Create the text file ~/.ssh/config
Put the following block for each key.
Host holds an alias for your ssh config. Now to connect to a particular server just envoke ssh shortname