How to add a signature to Outlook 2007
[Visual how-to located below.]

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1. Click on Tools > Options > 'Mail Format' tab.

2. Click on 'Signatures' button, 4th option from the top.

3. Select email account from drop down under 'Choose default signature', this will be the account this signature is assigned to.

4. Under 'Choose default signature' select 'New messages' and choose the proper email address. [Any new emails will have this signature added to them.]

5. Under 'Choose default signature' select 'Replies/Forwards' and choose the proper email address if desired. [Any replies or forwards will by default have this signature added to them.]

6. Click the 'New' button.

7. Type in a label for this signature, ie: person's name. Click OK.

8. Enter pertinent information: Name, phone, email address.. etc.. 

9. Click the 'Save' button.

10. Click 'OK' and then click OK again.

11. Click on New Email to see the results of your signature creation.

In addition...
Email addresses and web addresses can be 'hyperlinked'..
Images and logos can be inserted and 'hyperlinked'..