One: Be absurd.
Think about your favorite book or that seemingly boring idea that popped into your head this morning. Push it to the extreme, even if its absurd. When you push an idea out of its comfort zone, you will find that new connections are made.
Two: Always listen.
Another great way to generate ideas is to listen carefully to conversations other people are having. I know that your mother told you eavesdropping was not polite, but listening to others will help you generate ideas and make your writing better.
Three: Play a game.
Any game that excercises your imagination will do, but there are two in particular that work really, really well. When you are alone, use StoryCubes to generate writing ideas. Even if you are a non-fiction writer, excersising your creativity like this will surprise you. If you are in a group, play Quelf. It is the oddest group game I have come across and it will force you to break out of your comfort zone repeatedly.
Sit in a quiet space, commit to half an hour of complete silence without any distractions. Let your mind wander and your subconscious will go into overdrive while enjoying a nice break from the hustle and bustle.
Five: Read Weird Books.
I love the odd and the unusual, and there are thousands of ideas that can come from one good book. Read something out of your normal routine and you will be surprised what can come of it. Here are some ideas to get you started: Celebrations of Curious Characters, An Incomplete Education, & The Supper of the Lamb (A Theological Cookbook).
Six: Move Around.
Change your environment and be sure to bring along a notepad to write down any ideas you come up with. Visit a place that you loved as a kid, like the zoo or a carnival, or take a trip to see that museum in your hometown you never got around to seeing. Forcing your environment to change will generate more ideas.
Seven: Just Write.
Sit and write and write some more. There is something about putting a pen to paper (or your fingers to keys) that sometimes works almost without you. Two great books that expand on this technique are Accidental Genius and Write Now!