RebirthItemTracker
This uses the log.txt file to track item pickups in Binding of Isaac: Rebirth. This is particularly useful for streamers, so their viewers can see their items, but can be used by anyone. It's easier to see what items you have on the tracker than it is on the pause screen, and it also shows you stats for the item when you pick it up.
Here's a screenshot: http://i.imgur.com/BOjJ9WT.png
Download it here: https://github.com/Hyphen-ated/RebirthItemTracker/releases (get the latest file that doesn't have "source code" in the name)
To use it, first extract that zip file so the RebirthItemTracker directory ends up the same folder as Rebirth's "log.txt", then run the exe inside.
log.txt is usually at c:\users\ (you) \Documents\my games\Binding of Isaac Rebirth\
You can right click anywhere in the window to get an options screen.
You can mouse over items you've picked up to see their stats again, and click on them to open platinumgod.co.uk in your browser for more information about that item. (arrow keys and enter also work.)