Ask HN: How do you use Twitter for hacking?

I have mostly been ignoring Twitter for the past years, but now figure it's worth trying out. However, I don't need yet an other way to waste time on the internet and have no interest in daily life of most celebrities. So, share with me and everyone how you use Twitter for things related to programming and startups. Learning, sharing ideas, asking questions, finding collaborators, jobs or employees, getting customers, anything like that.