Windows 8 drivers for a number of eMachines notebooks and desktops are available via their normal support site which I've linked to below.
eMachines lists a number of Windows 8 compatible systems on their Windows Upgrade Offer page. Your computer not being listed doesn't necessarily mean that it won't function properly with Windows 8 installed.
Windows 8 drivers for a number of Gateway desktops, notebooks, netbooks, and all-in-one computers are available via Gateway's support site, linked below.
Gateway lists a number of fully or mostly Windows 8 compatible systems on their Windows Upgrade Offer page.
If your Gateway computer is not listed, it doesn't necessarily mean that it won't work with Windows 8. The default drivers included by Microsoft may work without issue on your computer.
Windows 8 drivers for HP laptops and desktops (including "touch screen" desktops) can be downloaded from HP's standard support site, linked below.
Many of HP's computers have both 32-bit and 64-bit Windows 8 drivers available.
Tip: Looking for Windows 8 drivers for your HP printer? See the HP entry below for special information pertaining to HP printers in Windows 8.
Any available HP printer drivers for Windows 8 are downloadable from HP's standard support and drivers page, linked below.
The huge majority of printers and scanners manufactured in the several years prior to Windows 8's release will have a driver included for it in Windows 8 or will have a driver available direct from HP. This includes many popular HP Inkjet, Designjet, Deskjet, LaserJet, ENVY, Officejet, Photosmart, PSC, and Scanjet printers, scanners, and all-in-one devices.
From this page, you can see if your specific HP printer or scanner will work with a native Windows 8 driver (in-operating system driver), via an update from Windows Update (Windows Update driver), or from a Windows 8 driver downloaded directly from HP (full-feature driver).
HP's Printing in Windows 8 page is also very helpful.
The latest Intel Chipset Windows driver for Windows 8 is version 22.214.171.1247 (Released 2013-10-14).
This update isn't actually a Windows 8 driver, it's a collection of INF file updates which help Windows 8 properly identify Intel chipset hardware like USB controllers and other hardware integrated on Intel motherboards.
This single update works with both 32-bit and 64-bit versions of Windows 8.
Windows 8 drivers are available from Intel (via their support page, linked below) for a number of their devices, including motherboards, graphics processors, network hardware, and more.
I have yet to see a nicely organized list of Windows 8 compatible Intel motherboards or other hardware, but I'd expect anything manufactured in the several years prior to the release of Windows 8 to be fully compatible.
Windows 8 drivers for hardware included in Lenovo desktop and laptop computers can be downloaded via Lenovo's support site, linked below.
See Windows 8 Upgrade Capable Systems for a list of Lenovo computers that they have determined are compatible with Windows 8.
Note: Lenovo also hosts a Windows 8 discussion board here if you're having trouble finding or installing a Windows 8 driver for your Lenovo product.
A number of Lexmark laser, inkjet, and dot matrix printers are fully compatible with Windows 8. See their Windows 8 Device Driver Compatibility List for more information.
Most of Lexmark's printers are supported natively by Windows 8, meaning a driver perfect for your Lexmark printer came included with Windows 8. A few others require Windows 8 drivers made by Lexmark, which you can download by locating the page for your printer from Lexmark's support site, linked below.
Microsoft doesn't just make operating systems like Windows 8. They also sell hardware like mice, keyboards, webcams, and more.
Windows 8 drivers for Microsoft's products can all be found via the individual product pages found on on their Microsoft Hardware Software Downloads page linked below.
Microtek's newer scanners and other products have Windows 8 drivers available, all of which are available from their support link below.
Microtek has no plans to release Windows 8 drivers for their older, but very popular scanners. If you have an older Microtek scanner that has a Windows 7 driver available, try that.