Is there an easy way to switch the current spelling dictionary in Cocoa apps without doing fancy mouse click work? And at the same time resetting the “spell check while you write highlighting”? I frequently need to switch between german and english dictionaries…
Another cool thing would be a) auto discovery of the language or b) a use of both dictionaries at the same time.
I have been playing around with CocoAspell for a while, too, but somehow did not like it. The Prefspane was too tedious and settings would not be sticky… and I would rather use a “real” OSX solution than some weird hack for something else ;(
If there are no answers to this: please Apple Engineers consider this as a feature request! 
You can choose “multilingual” as the spelling dictionary. As far as I can tell this actually checks all installed dictionaries, which is certainly not optimal (I for one don’t really care if any word I type exists in Portuguese), but it works pretty well for normal use. Certainly better than just having one language at all times at least.
Thank you Anders, this was the solution. But then I have moved to Spell Catcher - much cooler