3 answers
+1 Jeff
To that...
Per this (https://help.salesforce.com/apex/HTViewHelpDoc?id=customize_mapleads.htm&language=en" target="_blank)Training page:
If you set up custom Lead fields, you can specify how that custom information converts to custom fields in Accounts, Contacts, and/or Opportunities. In other words... For each custom Lead field, you can choose a custom Account, Contact, or Opportunity field into which you want the information inserted when you convert a lead.
As you can see in the image below, I'm actually mapping a custom Lead field to a custom Opportunity field.
Good luck!
Thanks,
Ben