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 ascii and the other way for any string input.
Convert text to decimal and the other way for any string input.
Make sure your passwords are good enough.
Get details of any file type, such as the mime type or last edit date.
Get the web-host of a given website.
Get the gravatar.com globally recognized avatar for any email.
Check if the URL is banned and marked as safe/unsafe by Google.
Get & verify the meta tags of any website.