Over the past decade, I've seen a whole swathe of applications replaced by services that run in the browser, so much so that nowadays, most of my working day is spent in front of my browser of choice -- Google Chrome.
Email can be a real rabbit hole. Open up Gmail in a tab, and an hour's gone before I blink.
Checker Plus for Gmail allows emails to appear as pop-up notifications, giving me an at-a-glance view of my email without needing to open up my whole inbox. In addition, I can use the preview window to read, archive, mark as read, or delete emails without leaving the current tab.
There's even an option to run this in the background when Google Chrome is closed and still get new email alerts.
If you ever wonder, "Where did my day go?" this is the browser extension for you.
RescueTime tracks the time I spend in an active tab or window of Chrome (or on a ChromeOS device), allowing me to see what I've been doing all day.
RescueTime auto-categorizes sites I visit and scores them on a scale ranging from Very Productive to Very Distracting. I can easily fine-tune the defaults and also pause RescueTime if I'd rather not have my time monitored.