I often run into the situation where I visit the page of a WP site that I need to update, then I open a new tab with the same domain and manually type the /wp-admin/ path behind it to login, login, then come back to the previous tab and refresh it to find it in logged in state. This should be easier! So I thought of making either a chrome extension or a bookmarklet to semi-automate the process. The bookmarklet was the easiest (and cross browser).

What it does

• While on any page of a WordPress site (not logged in), you click the bookmarklet
• It directs you to /wp-login.php where you login as usual
• You automatically get redirected back to the previous page

To grab it, drag this link into your bookmark bar:
WP Login

Note that this assumes your login page lives at the default location /wp-login.php

Update (21 jan 2017)
This one sends you from the site view to /wp-admin/, so in most cases you can safely hide the admin toolbar while viewing the site: WP Admin