A lot of teachers boast awesome professional development using Twitter because Twitter offers a few things that makes it powerful. It's a well known social media network. Once a teacher gets used to the flow of information through hashtags volumes of information can be had daily. Cybraryman has indexed over 300 education hashtags so it is near impossible to follow everything, however a teacher should choose the ones closest to his/her interests.
Following educators is essential. Don't know where to start. Twitter4Teachers is a wiki that catalogs educators into categories. Follow a variety of educators and those similar to you. @edcocp is the official Twitter handle for Connected Educators and is a good place to start to get to know educators and resources.
Wikis are another great way to enhance PD. They offer the ability to iterate content and methods with others from around the world. This unique feature connects educators to one another in ways that F2F interactions can not. Wikis also offer a teacher choice - choice to expend energy where they want to, choice to make a difference in areas they are passionate about, and the choice to make their voice heard.
PD may deepen a teachers craft through online interactions, but the interactions have to be meaningful. PD is meaningful when the teacher attaches importance to it.