Weird I was just typing Psyllium Husks into a post just before I read this thread (I spelt it wrongly though !
In addition to the places you mentioned I also throw a few tablespoons into the following and haven't ever noticed them :
Cake / Muffin mixes (with the baked goods start off with a tablespoon and then increase per trial and error as they soak up a bit of moisture)
Soups - (I've hidden cupfuls
Pudding type desserts
Pretty much anything that's a bit gluggy takes the husks surprisingly well.
If your not already onto it LSA is another similar product that's a great "sprinkle" thing. it's Linseed, Sunflower and Almond meal and full of all the omega's. A little harder to hide taste wise but very very good for you.