Safelinking.net is a free online service that helps you protect your links from inconvenient people or automated robots (crawlers) with security such as a CAPTCHA or a password.
Keeplinks protect your links by hiding them and shorten the url. Links can be protected by password and captcha
RGF link protection and link shortener.
A free URL shortening and redirection service that can turn a long URL into a very short and easy to remember URL