handy tools for site building??

I'm working on building a site and have someone who is doing a lot of the work. I feel like some of it might be redundant, and would like to know some of the common resources used. I also appreciate many of the sites that seam to have this no nonsense sign up and use process.

the site I'm working on will be a classified ad site, and bitcoin will be the primary payment option. Also need to know bitcoin api integration and security practices for running the site's wallet.

is there a list some where of the basic opensource things to add when setting up a site?

things like openid, a captcha, social media share buttons?

also things like the auto geo location, and I'm sure I'm missing a lot of the nice little features.

I know some stuff has to be done by hand, but why go re-invend the wheel when its already done.

only places I currently check out on occasion are github, sourceforge and softpeida's scrips area.