This Chrome Extension allows you to manage your YouTube history independently across multiple accounts and browsing sessions. It shows the 5 recently watched videos, with quickly accessible hyperlinks to launch the videoes. The options page includes a history of all videos watched. An additional feature is the ability to download an MP3 formatted file of any YouTube video, which is readily accessible from the popup menu.
Simply click the .crx file or drag it into chrome://extensions. For auto-updates, download from the Google Extension store.