Here's something I often need, especially when I need to find out when/why some server rebooted...
To get the system uptime, type this:
systeminfo | find "System Up Time:"
And in general, looking at the results of
systeminfo is pretty interesting as well, showing stuff like product ID, uptime, type of processor(s), system directory, language and regional settings, physical memory and page file settings, installed hotfixes, basic network parameters.