Archive a single giant table from a SQL 2008 database - filegroup backup?
I'd favour a BCP extract.


BCP export to file.
Import somewhere (different database or server) to confirm the file "is good".
Archive multiple copies, to multiple tapes.


@Marian answered a question of mine with a great list of BCP references that you might find useful. The BCP Basics by SQLFool is also a good starter for ten.