I've managed to do hollandaise in my blender a few times and it came out perfect. I used a Food Network recipe: http://www.foodnetwork.com/recipes/f...se-recipe.html
Marcela Valladolid (a FN chef) did a Mexican-style hollandaise in a blender on her show once. She added a couple of chipotles en adobo and I believe lime instead of lemon. Don't quote me on that last bit though.