Here's a list of websites around DOS and Windows 3.x that still exist… for now.

• Win31.de - This is still one of the best sites with resources and downloads for Windows 3.x, it has existed for a looooong time and I hope stays like that for many years to come.
• Stephan Großklaß' Homepage - It has some good resources around computing and Windows 3.x as well the Win32s compatibility list, which is super useful.
• MDGx Max Speed - Full of interesting resources aroudn Windows 3.x and other things.
• Calmira - Calmira was a replacement shell for Windows 3.x that makes it look like Windows 95. I've used it a lot in the past, I don't currently use it anymore because if I want the Windows 95 UI I install Windows 95, but it is a great piece of software.
• CalPaint - Like the Microsoft Plus! package for Windows 95, CalPaint adds themes to Calmira, you can use some of the pre-defined ones, or create your own.
• OldOs - Another great website with resources around Windows 3.x and other retro computing stuff.

A list of websites that are interesting here even though they are not necessarily related to Windows 3.x

• GUIdebook - This website is focused on showcasing Graphical User Interfaces, it's an interesting resource.
• SillyDog701 Netscape Browser Archive - This is the Netscape Browser Archive by SillyDog701, the pages are still up but a lot of the links are dead.
• Evolt Browser Archive - This website contains TONS of retro web browsers, it's actually crazy how many there are that I haven't even heard about. Yes, there are browsers for Windows 3.x for download.