Like Biz Bot, they offer links to the products they list. Once you choose a vehicle for delivering your message, you need to decide on the message itself. Give some thought to the second part of this seemingly simple equation. If not, don't be misleading. If you will only contact those candidates whose skills match your immediate needs, say so.
People appreciate knowing where they stand.
Try to be as specific as possible regarding your follow-up policy, while remaining general enough so that your letter works for all or most candidates. While delivering your message in a clear, concise manner is the primary objective of your correspondence, a properly worded letter can also serve another purpose. Your letter is an opportunity to introduce your organization. This doesn't mean providing details about your operation. It's more subtle than that.