I hope they will soon give an address, and phone number where donations can be made by those who cannot, or prefer not to donate online.
Go to FriendsOfFredThompson.org (unofficial site) and click on the link to in the fundraiser letter -- it will bring up a form to fill out that includes the address. If you postmark it by Monday and date the check June 4, you'll be counted as a "first day" contributor.