Each gadget now has its own post. Look above this one!
For the scripts you'll need some way to run them. For Firefox, Greasemonkey is the standard; on Chrome, I use Tampermonkey.
For userstyles, the easiest way to use it is to get Stylish, a Firefox/Chrome extension. Get it from the download links on this page.
If you have any feedback at all, please let me know so I can make things better! Also, if there's anything else that I can do to make the forums nicer to use, feel free to make suggestions, and I'll get to them when I can.