Upload a backup file made with the Nokia PC Suite.
On Windows these reside in C:\Documents and Settings\username\Application Data\Nokia\ContentCopier\ and have a .nbu extension.
After submitting, you will get a ZIP file back with a VCARD for each Contact. Good luck!
Confirmed to work with backups of Nokia 6100 and 5500, created using Nokia PC Suite v. 6.82.