How to Export from Your Browser, Import into Passpack

Firefox

You could use this script or, much easier, install the Password Exporter, a dedicated Firefox extension by Fligtar. It allows you to export your saved passwords to an XML file. You'll need to convert that to a CSV file, then follow the instructions to import into Passpack.

Explorer

IE Password View to extract all the passwords stored in your browser, and can export into several formats, including tab-delimited text files (TSV) and XML files. Then follow the instructions to import into Passpack..