There is a new website/service that takes care of most of the issues regarding tax/social security/insurance etc.
http://quitt.ch/
I haven't tried it out yet but it looks all right. They take a 8.4% commission, which doesn't seem too bad considering the hassle you would otherwise have to do it on your own.
And the Website is even in English :-)
P.S.: The service seems quite new so I'd be interested to hear of anyone who has actually used it.