POP3 I believe.
well you can create a new profile in outlook, get the pop setting from work (incoming@blahblah.com outgoing@blahblah.com)and just add them to your home pc. Also be sure to leave a copy on the server so you don't sync and pull all the mail to one spot.
the pst file would not keep you up to date, so i doubt that is an option, you would have to take a pst home everynight. Also, Outlook 2003 has an awsome web client why not use that from home? Same look