Here is a collection of sites that have a collection (holy collector) of blinkies, 88x31 buttons, stamps, or more!

cyber.dbamos.de, a collection of more than 4,000 88x31 buttons
hellnet.work, an archive of 31,119 88x31 buttons!
exo.pet, very cool homepage, just scroll down to find the buttons!
88x31.nl is a collection of over 4,500 88x31 buttons
pixels.crd.co is a site with a collection of small pixel sprites
pixels.crd.co's sister site dedicated to dividers!
a bunch of stickers

Collection of sites that focus on site responsiveness!

Responsive Website Design Tester, shows what your website looks like on different screens!