This is a simple, but helpful article about getting some tone in your midsection. As they state in it, most people think that just doing tons of sit-ups and crunches will get the job done but there's a bit more to it. It's a quick read, some good basic info to be aware of if you're goal is to get some toned abs though.
***Also, as an added note...if you're into lifting and working out, Muscle&Fitness magazine is a great magazine to look into. Most fitness magazines are just a ton of supplement ads and random BS, but M&F does a good job of putting in new routine ideas and other helpful information.