You can now create and share search queries that resolve to the current user by using the @me search syntax.
For example, navigating to https://github.com/search?q=is%3Aissue+state%3Aopen+assignee%3A%40me (when logged into GitHub) will return all the open issues that are assigned to you. You can also type assignee:@me is:issue state:open into any search field to return the same results.