There's this book called The Writer's Portable Therapist. What it has you do–free-writing excercises for twenty minutes–you could do on your own, but it offers some great prompts and some straight-to-the-point advice.
If you'd rather not spend twelve dollars on the book, here's how each excercise goes (the author calls it the "Free-Flow Writing Method").
Five-minute breathing exercise:
Breathe in for a count of five. Hold it for three. Breathe out over a count of seven. Breathe from the diaphragm, nice and slow and even. Do nothing else these five minutes. Clear your mind of distraction; maybe listen to soft music but other than that nothing.
Twenty-minute writing exercise:
Write, by hand, for twenty minutes. Do not correct spelling, do not revise or edit. Just write. If your brain blanks out, then write nonesense or (as I did) "I'm thinking" or "I'm stuck" over and over again. If, after twenty minutes, you want to keep going, keep going. But don't stop until you've cleared twenty minutes.
It worked for me. I was having an emotional slump and spent some time with this book. If nothing else, it allowed me to let some of the poison out, so to speak, and got me writing again.