Things that have helped me get my creativity and/or productivity back on track:
1. focus...usually I get bogged down because I have too much to do. When I focus on one or two things that I can get done today, it narrows down the list and then crossing them off is motivation in itself.
2. exercise...go for a walk, putter in the garden, play catch with the kids, shovel snow, mow the lawn. It clears your mind and invigorates the body.
3. get out...go see a friend, change your surroundings, go shopping for some little treat.
4. stop planning...I am often guilty of spending so much time planning that I never get to the actual doing part. Not everything has to be planned to distraction and learning to allow yourself the freedom to fail is a big part of that realization.
5. remember the passion...think about why you love what you do, forget any negative thoughts and concentrate on the positive. Think about the benefits, not the difficulties.
Slumps are part of the normal cycle of things. They come around from time to time, sure, but they always go away again. :D