TinyURL.com – where tiny is better!: Make your URLs smaller. I think this is a simple rediection lookup.
“By entering in a URL in the text field below, we will create a tiny URL that will not break in email postings and never expires.”
Entering two URLs immediately after one another resulted in “http://tinyurl.com/h3r6” and “http://tinyurl.com/h3rj”, so they must just have a simple, two-column lookup table. I initially entered the same URL, but they must check for dupes because it generated the same TinyURL for both.
I worry about services like this because what happens if (when?) they go under? A whole lot of URLs around the Internet are going to start breaking. MakeAShorterLink.com does the same thing.