As promised via PM, I have attached a product that will give you two additional text input fields, below the title field for new threads. You can set in which forums the product is active, and for which usergroups.
The two input fields use pattern recognition to try to ensure valid text is entered. There are settings where you can modify the pattern.
The links are built and displayed beneath the content of the first post in the thread, but they aren't actually part of the post in the database. You can control the color of the links with the StyleVars.
This product adds a table to your database which stores the threadid, and the two links for any thread having links associated with them.
Please let me know if you have any issues, or would like additional features.