What is currently the best way to purchase Mastercoins?
Are there exchanges out yet?
Do I need some special Mastercoin-Address/Wallet?
The best way for you to purchase the funds are to go to http://www.buymastercoin.com/ and make a purchase as described on the site.
Or just go to the google spreadsheet that is used as a sort of an exchange where you can purchase from the MSC holders themselves: https://docs.google.com/spreadsheet/ccc?key=0ApGPLGUd5ZCzdHFxbnhHQjBDSDVKamY5UHlWdkNMNWc&usp=sharing#gid=0
No need for a special Wallet but it is definitely recommendable to make a new address for the Mastercoins