Like all people, I love a present that has been well-thought out and picked especially for you. But sometimes money really is the best option. Sometimes people really don't have a clue what you want, and sometimes they ask and you don't even know yourself. As much as it's great when people put the effort in - there's respect to be had for people admitting they just aren't going to get it right. Also, It's nice to get to pick your own presents sometimes; a gift of money is a gift of guilt free shopping.
I have always held the opinion that when somebody gives you money as a present it should go accounted for. Often I don't tell the giver where it ended up, but you should know for yourself so that you can appreciate it more. Money given to you can easily slip through every day life without being remembered, but this shouldn't happen to a gift. I'm not saying keep the cash aside, I always forget to take the note shopping with me, plus if you need cash and you have some you might as well use it. Just know in your mind that you have a present to spend - think of it differently than other money, it is a present. Use it for something special.
It may be that you want to spend it on something mundane to lighten the load - but let it be specific; a takeaway treat if you don't feel like cooking, a weeks shopping, a coffee with a friend, a months phone bill, a new kettle or toaster. Treasure it.
I was given some money from my grandparents at christmas, and I knew I wanted some more clothes and accessories, so I used it for some guilt free shopping. I have accounted for the exact amount they gave me with some recent purchases. This time I felt I would let them know where it went and show my gratitude for it. I believe my presents are quite pretty and so I made a nice picture out of them which formed the design of the thank you card.