As a freelancer :

Project management : BaseCamp

Personnal GTD improvement : RescueTime

Invoices & estimates : Freshbooks

Accounting : my accountant uses Simply Accounting (Windows app on my vmware box)

Files : dropbox

Source control : Git on RepositoryHosting.com (6$/month and i can manage any number of SVN/Git repositories. And it just works)

Synch iCal with google calendar

Synch contacts with Plaxo

Thanks for the tip on RepositoryHosting :-)

Their price rocks.