When your employment ends with one company, it is important to purge all your personal information and connections from the employer provided machine.
Keychain Acces: purge all stored passwords and keys
MobileMe: deauth computer, stop all syncs after final clean sync, purge data
Adium: backup all the chat/message logs and then purge them from the machine, delete any accounts that are not work related
Mail: remove personal accounts, purge mailboxes, remove outbound mail relays, scrub rules and signatures
Address Book: backup and purge personal addresses, remove personal search feeds (LDAP, Open Directory, CalDAV, etc)
iTunes: deauthorize work computer, remove stored password and account name, back up and purge any local music/podcasts/videos
Terminal: purge .ssh/config tunnels/proxies and any stored keys
Dump all Web Browser Caches; clear Forms Complete, stored Passwords (not all browsers use keychain), purge cookies
Dropbox: remove your dropbox and XMarks and Delicious sync credentials
iCal: remove personal appointments, remove sync
Files: check folders in home directory for personal stuff; clean it out, empty trash; ditto on any network shares
Skype: clear stored accounts.
Update the outgoing message on your company voice mail box.
Update contact information on company databases, web kiosks, contact lists.
