Finding inspiration, I find, is largely a matter of paying attention to your own responses. If something seems to resonate with you at a given time, look into it. Don't try to force it. Looking for inspiration in something that doesn't excite you is like rooting around for a diamond in a big pile of cow sh*t. IOW, you're not going to find it.
If you pay attention to what you innately respond to, though, that's a good way to get clued in to what is really going to get you going if you don't already know what inspires you already. Even if you do, this sort of mindfulness is still a very valuable exercise as we all change over time and what inspires us today may seem dull and lifeless tomorrow. Pay attention long enough and you begin to be able to make connections between the things you like and this points you toward yet more potential inspiration. We collect these little points of reference over time, and eventually little clusters and connections yield a greater, emergent meaning that can tell us a lot more about what we love, why, and likewise similar things about ourselves. It's a road map to arriving at a gestalt of inspiration unique to our own experience.
For me, it comes from all sorts of things. In non-photographic art it's people like Caravaggio, Titian, Raphael, Rodin, Picasso, Anselm Kiefer, Gerhard Richter, and Lee Bontecou. In photography I look to people like Herb Ritts, Jock Sturges, Mark Seliger, Mark Laita, Phil Marco, Art Kane, Bert Stern, Nobuyoshi Araki, Eikoh Hosoe, Daido Moriyama, and Shomei Tomatsu. In literature it's Vladimir Nabokov, Osamu Dazai, Jeff Noon, Neal Stephenson, William Gibson, John Shirley, Kafka, and Allen Ginsberg. In philosophy/spirituality/intellect there's Kant, Nietzsche, John Daido Loori, Thich Nhat Han [sic], Robert Pirsig, Leonardo da Vinci, etc. The list could go on for dozens of pages. Most of these are things that I've arrived at through the process of paying attention to my own inner responses, which are sometimes very subtle and easily missed.
What I'm getting at is this: the key to finding inspiration is already in you. It's just a matter of paying attention and following the clues that are left you.