I wanted to add a Link to a related list, which would take the user to an external system.
Problem was, if I used a URL field, Salesforce.com wanted to show the entire URL within the Related List. This was so long that it drowned-out the other information.
With a bit of experimenting, I managed to create a Formula that produced a very small link.

How’d I do it? By using the HYPERLINK function.
HYPERLINK("http://www.website.com/info/ViewDetails.jspa?orderId=" & Activity_ID__c, "View", "_blank")
This lets me build a URL based upon some partial information in a record (eg ID number) rather than having to store the entire URL within the record.
The Bottom Line
- Use
HYPERLINKto make a URL instead of creating a field of typeURL