Well, I know this type of droplet's has been written before, but I have not seen much code shared. So here's my take on it. Do like this. Just drop your folder, or folders if you like, onto the app and all the .svn folders will be cleaned.
on open current_files
	repeat with current_file in current_files
		-- validate if the file as a folder
		if (current_file as string) ends with ":" then
				set current_file_path to (POSIX path of the current_file as string)
				do shell script "find  '" & current_file_path & "' -name '.svn' | xargs rm -Rf"
			end try
		end if
	end repeat
end open
I also added this as a gist under github. So please feel free to fork! https://gist.github.com/1063705