While you can't link up multiple google accounts to a single MapAList account, there is a way to accomplish what you're looking to do.
I would suggest simply "sharing" all of your spreadsheets that contain data you want to map with a single google account that you link to MapAList. All you have to do is go to
http://docs.google.com, log in with each account, check the boxes next to the spreadsheets that contain data to map, and click on the "Share - Invite People" button on the toolbar. You can then enter the e-mail address of the single google account that you linked to MapAList in the "Invite" box.
This will send an invitation to the single google account that you linked to MapAList and provide it with access to that/those spreadsheets. At this point, the "shared spreadsheets" will be available to MapAList since they are "shared" with the single google account that you linked to MapAList. Simply repeat for all accounts/spreadsheets required.
