|Where My Muse probably is right now|
Almost every writer goes through these phases. Your Muse, in fact, may be partying it up with mine right now. And they're not physical entities, so we can't exactly hop a plane to Mexico (don't we wish!) and haul them back by their scruffs.
What to do?
Well, for one thing, have a blog that you must regularly update. Because then, it won't matter how uninspired you are - you have to post something because you have readers, and your readers expect you to write. Even if you only have one reader, that's still a reader. Don't let that reader be all understanding about your inability to provide content. Advise them when they try that, "It's okay, I understand you're not feeling up to it, blog when you're ready" shit that it's not acceptable. They're supposed to be your cattle prod, not your enabler. So even if they think it's okay for you to slack off, ask them to lie to you and say that it is not. This will force you to come up with some words.
Do some reading while you're stuck. Or watch a movie, or go for a walk, or hang out with friends, or take in a lecture, or just about anything, really. Walk away from the blank screen and get some life experience. Do those things you're not allowed to do when the Muse is standing over you with a whip. Those things will, eventually, feed back in to your writing, and might just spark a little something.
Do something completely random and new, that you have not done before, while you're at it. Novelty may not always be pleasant, but it can shake loose some creativity.
Do creative things other than writing. Edit photos, play with collages, build models, sew, paint, make music, whatever. I've gotten myself through some dry spells by doing that. It takes the pressure off the writing side of your creativity so it can recover, while still building your creative muscle.
Make a little list. Break out the things you must write or do in order to write into manageable chunks, and do them. Force yourself to spend an hour working on said task, no matter how badly you feel you're doing it. Then walk away and do something else. Come back and take on the next thing on the list (or just pick the next thing that looks doable, no matter what order it's in). Lather, rinse, repeat, until hey presto - you've done some writing!
Organize your shit. If you're one of those writers who lets things get chaotic, now's a good time to put your writing house in order.
Read up on the bidness. Plenty of blogs and books out there that talk about everything from the nuts-and-bolts of storytelling to finding agents (if you're going the traditional route) to self-publishing to marketing and all points in between. If you ever want to make a living writing, you've got to keep up with the business side of things. During a bout of writer's block is as good a time as any, even if you feel you'll never ever write a worthwhile word again (you will).
And if you have to, if nothing's working, go do one of those writing exercises that are so often plastered all over popular how-to-write sites.
The Muses will return from Mexico. Eventually. And now you'll have at least a handful of pages to wave in their faces and scream, "While you've been drinking yourself into oblivion in the hotel pool, some of us have been working!"
That's always rewarding.