Useful terminal commands to quickly get system details

To check if your machine is 32bit or 64bit:
$ uname -m

Depending on the output..
i686 = 32bit
x86_64 = 64bit

To check the version of Linux you're running:
$ cat /etc/issue

To check the free space you have on each of your disks:
$ df -h

To check Memory usage by processes (like Task Manager):
$ top