Yahoo! Voices (previously Associated Content) is an excellent site. Yahoo exercises a little more editorial control, but I think the Yahoo domain is stronger and better at organic search engine rankings. You can also submit articles for up front payment (for which you'll receive a few dollars). This is similar to the apprentice program here, but there's no limit to how long you can participate.
The downside is that Yahoo! Voices doesn't offer things like Amazon or eBay capsules, which can be real big earners. It's a great place for purely informational writing that may not otherwise be commercial or marketable.
Squidoo, on the other hand, is good for highly marketable content. If you write things that promote Amazon products, for example, then you could potentially earn a lot of money there.
Personally, I've had better success at Yahoo! Voices than Squidoo, but I've also been a member there for years.
And like someone else said, you should write somewhere else as well as HubPages. Cultivate multiple revenue streams. None of these places are get rich quick schemes, and you'll make the most income by making a small amount in multiple places.