I use this page to keep track of pages about me elsewhere, e.g. profiles on various community sites.
In addition to helping me keep track of these sites, linking these pages from my site helps verify that these pages were authored or edited by me. If you see a page or user profile that claims to be me but isn't linked above, or that doesn't have a link to my site, it probably wasn't made by me.
Note that having a link in one direction doesn't prove anything: I could claim to be any user online, and any user can make a link to my site. There needs to be a link in each direction to confirm that the two identities are the same person.
(and even then there may be other issues, like someone cracking into my account and changing things without permission, or community sites changing ownership over time, invalidating the links I made above.)
Most links on this page are labelled with XFN's me
value, so machines can make more sense out of them.
Onxiam is a site to help users keep track of their identities; my account there is ger.