I googled for a plugin which enabled me to insert HTML snippets into posts and pages without fiddling around with the template files - and I stumbled upon Embedit Pro. When I saw that it hadn't been updated for more than two years, I already feared that it might not be working any more. But it doesn't need any updates, becaus it simply works, even with the latest WordPress version. It's so imple, yet so effective... Awesome!