Basically, is there a way to find out if those "really cheap" websites that no one has ever heard of are safe to buy from? is the product you buy the real thing? Are you safe from id theft?
That is certainly a danger. Fraud is a serious problem and Internet crime is one of the fastest growing crimes out there.
Even if you do recognize the name of the company, they could be "phishing" which simply means using a domain name that resembles that of the company but is different from the real one via: a common misspelling, an extra/missing hyphen in the domain name, etc.
Moreover, crooks like to trick you by making your status bar show something else than the actual URL when you hover over the link, and then change it in the address bar upon your arrival. Yes, they can do that, unfortunately. Web browsers seem to have been created by people who think that people do not lie, cheat, or steal - or that such people do not use the web.
That being said, there are a few things you can do.
Look at online consumer opinions sites. One example is the epinions.com web site and there are probably others now too.
You can go to your library, and see if the company has a Dunn & Bradstreet (D&B) entry. Go to reference section or microfilm/computer area of your local library to check this out. If you get stuck, ask a librarian or someone at the reference desk for help.
If you click on the order or the registration page, they should go into SSL mode. At that point, any decent browser will let you check the credentials of the site. Usually they call it the site certificate or something like that. Look for that. If they don't use SSL - hoo boy, do you really want to use their site even if they _are_ who they say they are?
You want to make sure the cert is good - not expired, and that it is signed by someone you trust, like Verisign. It's not an iron-clad guarantee they are who they say they are, but it is something. At least they have claimed it, and the claim has probably not been revoked - not if the cert is still valid and signed by a good/respectable CA. I am presuming that if they scam a bunch of people and are using SSL, someone will gripe to Verisign or whomever.
You can minimize your risks, if you are unsure, by buying their merchandise from someone you already trust and do business with online. For instance, Amazon. They have been around for a decade and carry a huge variety of products.
Also, you can use payment intermediaries with some sites. Like, I just now notice that Apple's iTMS web site says at this moment that if you buy an iTunes gift certificate with PayPal, you get up to 25 Free Songs. PayPal is pretty popular. Lots though not most web sites accept payment via Paypal. In some ways, maybe most ways, it is more secure than your credit card. That is that the worst you can probably be out is the amount of the purchase. They don't ever actually get to see your credit card when you use PayPal, I think.
It is a somewhat untrustworthy world out there. In some countries/cultures and neighborhoods, it is deemed perfectly acceptable to rip somebody off. It is a big status symbol thing. Obviously, law enforcement is lax/lacking in these areas.
Credit card fraud is a huge problem, costing billions of dollars per year. Be safe, protect yours.