I don't know what species are where you are, the best book on U.S. species is probably Carnivorous Plants of The U.S. and Canada by Don Schnell. Generally, aquatic utricularia are the most common, and are in many ponds, but are mainly noticeable when they flower (July-August I believe, at least around here). It can take a bit of research to find other plants, but if you can find hiking guides, they may give you some ideas on where to look. Also, if you hear of any parks with wetlands, bogs, or swamps, you might manage to find something. If there are any growers in your area, hopefully one will be able to help you.
If you're in Northern California, you might even be able to find Darlingtonia somewhere... they must really be something to see in the wild. I believe Drosera anglica may be in California somewhere, and I'm sure there are other native CPs. Sometimes a websearch will help find out what species, but it isn't easy finding places most of the time.