Dec 03, 2018: 3D Universe has removed most of his free items from his site, although several of the newer ones remain. Some of them may still be available through the Wayback Machine; check the freebie wiki.
Nov 11, 2018: Mr Sparky/Sparkyworld’s freebies have a new home at the Attic’s Free Zone. I’ll have some link updating to do soon…
Dec 12 2017: Looks like Chris Cox’s blog is gone (thanks to Nik for the heads up!) but the Wayback Machine has some of them archived here.
Oct 15 2016: Ironman13 has also removed all her free poses and props from freeposes.net. She has a few of them uploaded at Renderosity Freestuff. I did the usual strike-through text but left the actual link in case anyone wants to try their luck at the wayback machine archive.
Oct 09 2016: Looks like Pixeluna has removed all the freebies from her site.
May 16 2016: Updated the Buried Treasures page to include some old freebies for the equally old Sluggians. Battle Slug!
Also, the freebies from Mada’s old Faerie Dreams store can still be downloaded here; click on the “Faerie Dreams” link in the menu. Don’t know if the forum freebies will show up again.
Dec 04 2015: Updated the Buried Treasures page with newly discovered links to Front Tails Hair for Sadie and Boy Cut Hair for Sam. From The 3D Zone’s old web page.
Sep 17 2015: Arcebus has removed his website; the two freebie pages have been archived here and here, but not all the downloads work.
Sep 04 2015: Redviper’s “delivery system” moved to a new URL. I think I’ve updated all the links here, but in case I missed any, the new site is here.
Aug 27 2015: Added Bunny Girl for Toon Generations to the Buried Treasure Page, now that The3DZone’s site is mostly dead. Also, the recent site update at Renderosity broke links from the old Christmas Give-Away pages so they’re no longer available. But it was nice while it lasted!
Aug 23 2015: Fantasies Attic changed the URL on their free site and broke all my freebie links. Again. I think I caught all the changes this time around, but if I missed any, the new main page is here. Search works.
Nov 15 2014: Updated the Uniform Fabric Tiles to add some previews, which I somehow failed to get around to doing before. Also added a Buried Treasures page.
Nov 02 2014: Updated the Toon Hair Materials page to add previews…’cuz there weren’t any. o.O
Oct 20 2014: Added four new tiles to the Seamless Tiles page
RedEyeCat 
Vikke has a groundscape like that on her DA account. Here, I’ll get you the link!
http://vikike176.deviantart.com/art/Vikike-s-Ground-01-270472721
Thanks for the reminder! I keep forgetting Vikke had a website too. 🙂