Handy online tools
Tools for various uses.
GWhois
Unrelated to the gwhois
package available through the Ubuntu repositories, GWhois performs whois lookups in such a way that all domains can be found, even brand-new ones not available through other whois lookup tools.
icanhazip.com
Serves current IP address in plain text, which is the only content of the entire page.
[mailinator.com/ Mailinator]
Amazingly simple webmail server, particularly useful for testing user setups of packages. Also great for creating throwaway email addresses when creating online accounts without revealing a legitimate email address.