Mathematics educators are engaging in an online community referred to as the Math Twitter Blogosphere (MTBoS) to support their practices. Although studies indicate that educators who participate in professional online communities engage primarily in sharing and consuming resources, and in some cases also in building and maintaining professional relationships, it is unclear how they interpret these opportunities. This study explores the community building activities mathematics educators refer to when speaking about their engagement in the MTBoS and unpacks ways in which they value and establish value in the activities they refer to. Findings indicate that members of the MTBoS community refer to identifying and selecting resources frequently, that they value resources that are inspiring, relevant, and reliable, and that they establish values through identifying resources with attributes of specificity, like-mindedness, credibility, and through repeated exposure over time.