Can Muggles do Magic? In the cases you mentined, yes.

[peppermintfatty]

No: HPFGUIDX 41398

> 
> Now if a Teaset would work for Muggles, wouldn't an invisibility 
> cloak? Could Dudley fly a broom? Agreed Dudley's stupid, but could 
> you picture him finding Harry's potion book and trying to brew 
> something to make him lose weight?
For the most part I would have to agree with you. The cloak is a 
physical object constructed with it's own magical properties. There 
is no evidence that the wizard has anything to do with it functioning 
correctly. While I cannot think of the exact instances right now, I 
believe that the cloak has been used to cover up inanimate objects 
before. It would seem to me that it would have the same properties on 
whatever it covered. In the case of a broom, as can be found 
in "Quidditch through the Ages", the reason magical folk started 
using them was that they were inexpensive and would not raise muggle 
eyebrows. They also mention that those who were skilled broom makers 
traded their services with those skilled in other areas. This leads 
me to believe that a wizard broom, at least in the beginning, is 
nothing more than a muggle broom, with a charm on it. We have seen 
cases as with Harry's Nimbus 2000, where it flew off and hit the 
whomping willow, that a broom can fly without a wizard. In this case 
all of these facts lead me to believe that a muggle could fly a 
broomstick the same as they could the ford Anglia, with the 
difference being that they probably would not be very skilled at it. 
As for the potions, I agree there again. Potions nowhere in cannon 
have been shown to be magical per se...as with no incantations 
or "fancy wand waving"...they are concoctions made up of various 
objects, some of which are magical (i.e.: Unicorn Hair). If Dudley 
were to raid Harry's trunk and found a book of potions, as well as 
some of Harry's potions class supplies, I think he theoretically 
COULD produce some havoc causing potions. The only problems would be 
if things were labeled. If not, then Dudley, being a great git, would 
have no idea what was what. So I agree with you in theory, as neither 
broomsticks, the cloak, or potions seem to have anything to do with 
the internal magical properties of wizards, but instead the magical 
properties of the ingredients in potions, or the magical properties 
imputed by the wizards to the objects in question in regards to the 
broomstick and the cloak.