You can link to any store or any page you want on your hub as long as it meets Hubpages terms of service.
There's no problem with linking out to other people's pages without an affiliate link to provide your readers with more quality information. In fact, that's what the internet was designed to do to begin with.
When you consistently provide good content to your readers, they come back to you more often to see what else you've got to offer them. You build trust in them. So those one or two times when you offer a product with your affiliate link in it, they're more likely to click.
I recommend scouring the internet for some really good blog posts and articles related to topics that interest you, bookmark them on a social bookmarking site so you have access to then at all times, and link to them. Some people like to Twitter and Facebook them, too.
That's part of providing unique content, except that it's not yours and you're giving the author credit at the same time. Everybody wins.