The two best websites to shorten long URLs are TinyURL and Bit.ly. See below for a rundown of the shortening process:

TinyURL

1. Go to their website at http://www.tinyurl.com
2. In the box that says "Enter a long URL to make tiny," copy and paste the URL you want to shorten.
3. Click the Make TinyURL! button.
4. The new, shortened URL will appear at the top of the page and underneath the original address. Copy the new version of the URL and paste where desired.

1. Go to their website at http://bit.ly/
2. Paste your long URL into the long search bar (where it says "Paste a link to shorten it").
3. Click Shorten.
4. Copy the new URL from the search bar or click Copy (next to Customize).
5. Paste the new URL wherever you want.