If you are programmatically creating CSV files intended for Microsoft Excel users, and cannot figure out how to make URL data in the CSV files behave like click-able hyper-links for your users, this tip is for you.
There is a special format in which URLs should be formatted, that is used by a number of spreadsheet applications to interpret URLs as click-able hyper-links. The format is this:
=HYPERLINK("URL")
The URL must be enclosed in quotes for the format to be interpreted properly (without which, at least, Microsoft Excel complains).