Hi Jirka,
Maybe this one is something for you:
I put a little service called Spootnik (
http://www.spootnik.net) together which synchronizes Basecamp directly with OmniFocus. Each one keeps it's own OmniFocus database with his private/business tasks and share some of them (mostly business tasks) over Basecamp.
Spootnik is currently in private beta. If you like to test-drive it you can sign up here
http://www.spootnik.net/signup.html and join the private beta crew.
Best regards,
Lars