I've always been inspired by reading other books.  If I enjoy a story, I'm inspired to imitate the elements that I like.  If I'm frustrated because I can't find anything good to read, or I'm unhappy with the way a book was written, I'm inspired to write my own books to fill the gap.  Read books and 
study them.  Absorb yourself in what you enjoy, and tear apart the things that you read.  You can study movies and radio dramas, too!  I'm also often inspired by the talent that I read on the forums, like this one.  Seeing my peers pursue their wonderful ideas encourages me to go work on my own books.
Don't be afraid to take a break.  Sometimes, if you're in a writing rut, focusing on something else is the best thing you can do.  Is there something else you like to do?  (If not, may I recommend crocheting?  

)  Focus on it for awhile.  Sometimes only a day off is what it takes to clear the head and renew excitement.
There is a place for "forcing" yourself to write as well.  (Especially if you happen to have a deadline looming over you...)  From what I've been reading in writing theory books, most of the modern day masters will tell you - you can't always wait for inspiration.  You have to write even if you don't feel like it.  I've found this true when I was pressed with a deadline for a script; if I force myself to work on a story, it will eventually come.  Put aside all distractions; it's truly more productive to stare at your blinking cursor than to detour and browse the web!  
One book I read suggested that you put something - anything -  on that blank page.  Even if those first few sentences are junk, it's something - and it may help get the juices flowing.  If you typically write on the computer, switch to longhand (or vice versa).  If you're stuck on a scene, skip it and jump into the story somewhere else.  Try writing in a different genre than you usually do.  Try a different format (prose vs. poetry, or try screenplays).  Use a different POV.  If you're stuck on a particular story, try looking at it from a different character's POV.  Instead of the main character, try his mother, his brother, his best friend, or even his cat.
Another thing that repeatedly inspires me is the Bible.  You will not believe how many story notes I have scribbled while studying.  Verses will stick out to me - "That's exactly what this character learns," or "That's the theme of this story," or "That applies perfectly to this scene."  Some Scripture begs me to use it as a basis for a story all its own.  Allegory or "inspired by" is always an option.  You may even find a simple phrase of words that inspires you - the Bible is full of beautiful phrases that ring on their own.  (I like book titles that are phrases from Scripture and hymns, for instance.)  The other day while I was studying, I found several verses that may inspire chapters in my NaNo novel.  I read "When my foot slipped, your mercy held me up" (paraphrased) and thought "I could do a chapter where they almost fall off a cliff!"  And just like that, my thin plot starts expanding and I can't write notes fast enough.  God is good - He'll send the ideas in His time!  Ask Him.