While Marketplace and Freebie Galaxy are two of the best places for many free and inexpensive items, it is a matter of simply using the right search or finding the correct floor in most cases. Marketplace is by far better on free items than Galaxy, as it is much larger. There are others worth mentioning and exploring.
For free furry avatars check out the AX mainstore. They have a huge amount of old avatars for free. For textures, Nikita at Trianwe has a large selection of of textures, scripts and animations for free or cheap. Kuwait freebies has a number of textures, as does freebie Folly Limeta at Skidz. Arcadia Asylum. For those seeking free and low cost in the area of fantasy Grendel's Children and Phaze Demesnes are there for your needs if you are strapped for lindens.
For those looking for pony freebies inworld, check out Derpyland and, Illusions Garden. Please be aware these are General sims, so don't wear anything you wouldn't to a family restaurant. or act like you wouldn't in front of your children or friends' children. That brings us to well those looking for adult items. For adults with certain preferences check out Freebie Temple. Freebie Textures carry the obvious and more.
Other places to go for free items include, Freebie France, Freebie Bazaar, Freebie Barn, Freebie Street, Freebie Zone, Freebie Fever Freebie Island, Freebie City, Freebie Dungeon, Freebies the Rock. Freebie Factory as well and Freebie Sandbox. There is also the Freebie and Newbie area of Blackwater. There are also freebies at Equus near Areo Pines as well. Caribbean Beach has a number of free items including tattoos.
Last but farthest from least is the Enky's Dollarstore, which has many items for nothing or 1 linden. They even have tinies dragons, and dragon tines for free, which is hard to find. I know most dragon avs run over 1K so this was an exciting find for me personally.
Unfortunately a few Freebie places have closed. Freebie Market is no longer in business. And two stores, LS and aquarium freebies no longer carry any free items I can tell..
Please be aware than any oversights with regard to listings were not intentional except when the subject matter was too adult-oriented for the paper or cases where mentioning a single freebie or two would be basically offering free advertising space for a store. I hope everyone enjoys reading about these places as much as I have enjoyed exploring and writing about them.