There are sites like that. For example, this one.
Moz will remove the "nofollow" from your profile and first custom URL once you accrue 200 mozPoints, presumably because you have shown yourself to be a trusted contributor.
The question remains however as to how much this is worth in Google's eyes. Since I work for a financial publishing company those links probably are not as useful as they might be to someone who works for an SEO company, since they are not directly relevant.
Guest posting and commenting used to be big link-building strategies, but not so much anymore.