The letter meme--
handhold gave me M!
I've already mentioned metaphysics, motorcycles, and muscle cars so:
Money, it had to be said
Meditating, which completely makes up for the materialism of the last one
Mindfuck movies
Music, nearly any kind
Mushrooms
Magnolia
Mountains
Messages in bottles
Moon
Miles in a car
Muscle-bound men
Memories
Momentum
Morpheus
Mercury (weird, but when I was little, it was my favorite planet. I don't really know why)
Mud
Marilyn Monroe
Monet
Mexico
Morrison, Jim
Mermaids
Mind
Mellowness
Main drag of towns
And the list goes on. :)) Comment if you want a letter, naturally.