Outlook contacts can be exported into .csv (comma separated variable) files and then imported into Google Contacts, but distribution lists are just groups of contacts. Unfortunately as of April 2011, there isn’t a way to export distribution lists as a group from Outlook, then import them into Google Contacts. Distribution lists have to exported and then imported individually.
It is easier to recreate distribution lists in Google Contacts from your existing contacts than to move each list. This assumes that all the necessary contacts are already in Google Contacts. Duplicates will be created if the procedure below is used to import distribution lists that contain contacts that are already in Google Contacts. This may still be useful if the distribution list has contacts that are not already in Google Contacts as the duplicates can easily be removed.