Certainly I write for a number of content sites. I don't believe one should ever keep all one's eggs in one basket. I started at Squidoo, and then found HubPages. Those are still my two favorite sites where I invest most of my time. Currently HubPages gives me more income.
I also write for some of the newer sites like Zujava, NetLeeks, Wizzley, and LoveBlinks. I have a few articles at Qondio, but have never made a nickel there and I don't invest time into it anymore. From time to time I contribute at Gather, but it doesn't generate income in the same way and it's really more of a social network. I write and contribute photos there sometimes, but have to stay away most of the time because it can be addicting.
I try to stay current on Squidoo and HubPages, updating when necessary and participating actively in commenting and other activities the sites promote (such as answering questions like this on HubPages.) I plan to gradually build the number of articles I have on the newer sites when I have more time. They all have good features, but there just isn't enough of me to keep putting content on other sites when I can't keep up with my own websites and blogs.