Google opened Knol to everybody after announcing it last year. Knol is another free web publishing tool in which author can earn ad money. Main point Google is trying to stress here is focus on authors. Moderated collaboration is allowed and encouraged. Most Blogs (TC, SEL) are comparing Knol with Wikipedia because of collaboration features. [...]
Hubpages Officially announced the traffic comparison with Squidoo. The data is surprisingly high for Hubpages. Monthly Unique visitors are comparable. But Squidoo has 4 times number of pages (lens) than Hubpages (Hub). So hubs receive 4 times more visitors than lenses.
Hubpages is another Web Publishing Service similar to Squidoo. Publishers are called Hubbers. Published Web Pages are called Hubs. You can add different Capsules (similar to Modules in Squidoo). Capsules can be Text, Video, Links, Photos. Hubpages allow monetization using adsense, ebay, and amazon.