There are lots of ways to find out what’s in the food you’re eating, including many apps like MyFitnessPal. Here’s another one and it’s really well executed:
Spe.lt is a Web app that instantly shows you nutritional information for whatever food stuff you type into the search box. It then allows you to add items to a list, totalling your consumption.
It’s simple, effective and rather beautiful. Note: The developers say in their terms that they collect the information you type into the box to analyze what visitors are interested in. If you’re happy with that, it’s definitely worth playing with.