What are some good places to sell photo prints online? Is it possible? What aspects depend on country, laws, or copyright restrictions?
It depends very much on what you are trying to accomplish. There are at least 3 broad categories, which I'll try and give some examples. Note that my examples are probably US centric, but the services might also have foreign affiliates, I haven't looked into them all, so...
Selling Prints to Clients
Okay, so you've done a photo shoot with some clients, and they want to order prints from you. Where do you direct them? This will depend somewhat on what country you are in, but here's a few.
Selling prints to strangers
So, you took an awesome landscape picture, and now you want to sell a print to a complete stranger. You could use the above sites, but you might have more luck with a dedicated site. The truth be told, however, is that unless you already have a fairly well known name, you're probably not going to have much luck online from this type of picture. I don't have much experience here, but I'll post a few that I've heard of.
Selling the rights to use your images
This is also known as stock photography. These photos typically either sell a concept, have a type of photo illustrated, but can include landscapes and other general interest pictures. There are at least 2 sub-categories here, I'm more familiar with the micro-stock site. Specifically, you can look into sites such as those listed below.
I would suggest you very strongly consider the pros and cons of the microstock model before submitting your images there. Generally speaking, micro is a model that's much better for the consumers than the producers of content.
If you'd prefer a more traditional stock photography model I would suggest you check out the Alamy agency: http://alamy.com/
I've sold prints on ebay in the past, however they have very strict rules (and a bunch of competitors ready to report you) about anything that could even vaguely be considered 'erotic'. One time I was banned from selling because the 'model was nude' even though all you could see where her head, arms, and legs. I'd like to know how the ebay moderator managed to sneak into my photo shoot to verify their 'fact'.
You will find a lot of competitors on ebay so your work needs to be top notch, popular, and competitively priced to get sold regularly but even then it's only a bit of extra money.