Convert text to binary and the other way for any string input.
Convert text to hexadecimal and the other way for any string input.
Convert text to decimal and the other way for any string input.
Convert text to octal and the other way for any string input.
Make sure your passwords are good enough.
Get the gravatar.com globally recognized avatar for any email.
Get details of any file type, such as the mime type or last edit date.
Check if the URL is banned and marked as safe/unsafe by Google.
Get the web-host of a given website.
Find A, AAAA, CNAME, MX, NS, TXT, SOA DNS records of a host.