What are some good project library resources? For instance, I'm looking for some online community / e-commerce software and I'd like to know what all is available out there, compare, etc. I don't know where to go to find large applications like that without searching directly for it.

I'd also like to know what popular blogging software there is, etc.... anyone have links they could share?

Also, they don't have to only list open source projects, i don't mind if these resources also list software you have to pay for.