I have a developer user id that was set up on force.com before my company was set up on Salesforce.com. I was invited to my company SF, but my email address is already in use - by my other account. So I setup a different userid using an abbreviated email address. Is there a way to merge my two user ids together?
Your username must be unique and be in the form of an email address, but it doesn't have to be a real email address. I would recommend you log into your developer org and change your login there. I use a naming convention such as email@example.com. Once you've freed up your user name, log into your company's org and change your login there. Both accounts can have the same email address.
You can't merge a user between two different orgs. The developer and production org (your company org) have nothing to do with each other and are silos except for a sandbox.
What sorts of information are you trying to move? Just the use of the email address as a login/userid at the salesforce login page?
Your email acts as a router into the org from the login page, you may be able to contact Salesforce and have them remove that 'developer' org so you can reuse the email as a login elsewhere.