Reddit mentions of First Peoples in a New World: Colonizing Ice Age America

The most widely accepted site so far is Monte Verde, at the southern end of Chile. Its main component is dated to 1,000 years before Clovis and is make up mainly of organic materials such as tent stakes, woven grass, mammoth hide, and food remains. An assembly of archaeologists visited the site (in the 90s I believe) and concluded it was valid. Its only real detractor was Stuart Fiedel (although David Meltzer more recently retracted his acceptance as well). This was a hugely important discovery because it showed that people not only got to the Americas before the opening of the Ice Free Corridor in Canada, but it also showed that people got to the southern end of South America by that time. Because of this site, most archaeologists now acknowledge that the first people to get to the Americas skirted along the west coast by boat down from Alaska.

Here are some other archaeological sites with pretty good pre-Clovis evidence (none are as well accepted as Monte Verde, but they are still likely legit): Meadowcroft Rockshelter PA, Cactus Hill VA, Friedkin TX, Paisely Caves OR.

Here are some that are more iffy and may not be pre-Clovis after all: Topper SC, Calico CA, Pedra Furada - Brazil.

These are just off the top of my head, I haven't even gone into the pre-Clovis butchered mammoth remains found around the Great Lakes and in the Great Plains, and all the other less well known sites in South America. As for the genetic and lingustic evidence, I am an expert in this field and even I have a hard time keeping up with what the latest theory is (probably because I have my head buried in my own dissertation writing). It seems to change every couple months though. I can recommend a few books that provide a general overview of work this field though:

David Meltzer's First Peoples in a New World is a good start. He's pretty much a Clovis-firster, so you'll get a healthy dose of skepticism after reading this book. It's very readable and sums up a lot of the past and present arguments that have been made for pre-Clovis in the Americas.

Then there's Paleoamerican Origins: Beyond Clovis, which is a more scholarly collection of research articles dealing with various topics relating to pre-Clovis research. This book includes sections on skeletal and genetic evidence, but keep in mind more recent research has been done on these topics as well. There's nothing on Paisley Caves or Friedkin in here either, which is sad, but the pre-Clovis components of those sites weren't published until a few years after this book came out.

Then for the heck of it, I might recommend Across Atlantic Ice: The Origin of America's Clovis Culture. This is the book on the Solutrean migration theory, which very few archaeologists accept, but I still think it's worth reading nonetheless. The hypothesis is well put together, and the circumstantial evidence behind it is interesting, so read it with an open but critical mind.

One last thing, in the SAA Archaeological Record, my friend Amber Wheat conducted a survey of archaeologists' opinions on various aspects of the peopling of the Americas. You might find this very interesting if you're trying to find out what the consensus is.

I can provide you with some additional sources for the archaeological sites I listed, as well as more recent research in genetics (I'm not sure about lingusticis, I haven't seen much on that subject lately), but I'm being lazy at the moment. But let me know if this is enough or if you need more, and I'll see what I can dredge up.