SQL Server 2005 - 2 sets of backups - 2 maintenance plans?
You probably don't want to put your backups in two places like that alternating.  You (probably) won't be able to do a point-in-time restore if one of your file store locations is lost.  You'll be stuck with the latest full backup of the remaining system.

DMason's suggestion is workable, but personally I would use the scripts from http://ola.hallengren.com/ and back up to a network location.  From there, you can backup up the files to tape or another disk.