p8recon allows you to easily explore your pico-8 game library: it renders all of your carts labels, spritemaps, and maps in your browser and can show the code for each game.
Note: this product is still alpha level.
If you use git for version control, it will render the above for each version of your carts.
Currently this only supports the .p8 format, but if people buy this tool and express interest I'll get started on implementing .png support.
You'll get p8recon, a tool to explore your pico-8 library.