There are lots of abs exercises that you can do without any equipment and that you can work on if you feel so inclined (hehe, I love my phrases) and all you really ahve to do is a quick Google search. A few that could whet your appetite...
Superman:
Lay down flat on your belly with your arms outstretched over your head. Lift your legs and arms a few inches off the ground and hold.
Dracula:
Lay down on your back with your arms either straight at your sides or laid across your chest. Lift your head and legs a few inches off the ground and hold.
That V thingie:
Lay down flat on the ground on your back with your arms straight above your head. Simultaneously lift both your legs and your arms (using your abs, of course, lift your entire torso-ish region as well) until you touch your legs. Keep those legs and back straight! Repeat.
Leaning Back Thingie:
Sit up straight on the ground with your legs positioned as if you were do a crunch (in front of you, knees bent). Extend your arms parallel to the ground. Lean back until you feel your abs working. If you don't feel anything... go lower! Keep your back straight and your arms extended. Hold.
Those are the ones I like I remember off the top of my head, but like I said, more are only a Google search away!