Sometimes it can be really hard to come up with ideas for new songs. You may find yourself, as I often do, simply repeating the same chord progressions over and over again, and you're afraid that all your songs will start sounding the same. Here are some things that I do to get myself back into the creative flow:
Listen to New Music - I have an article on introducing yourself to new musical genres. Follow the steps in that article and you'll no doubt gain several ideas for new songs. Listening to interesting new music always gives you a new perspective on things. Everyone else in the world looks at things a little differently than you do. A piece of music represents one artist's or group's point of view. By continually stimulating yourself with new viewpoints, you will always be able to see everything differently, even that keyboard sitting in front of you.
Try writing in a different genre - I covered this a lot in Don't Find Inspiration: Create it. Writing a different genre than you usually write in will give you something new automatically, plus you'll learn a lot while you do it. Pick a random genre or combine two different genres that don't normally go together. You can get some weird and interesting results, and they will always be creative.
Play with more obscure chords - Break out your old books and look up some of the more esoteric chords in them. Like listening to new music, hearing new chords will give you a fresh perspective. Try combining chords in ways that you haven't tried before.
Mess around with some pre-made loops - If you have the ability throw together some looped drum tracks or chords on your workstation, dig through the presets that you have and put some together. You'll have instant accompaniment while you try to play new stuff. It really helps get things flowing quickly.