Looks like you surfed by some websites that download you more than just the data you wanted to see. Doubt that one vapeshop would sell your data to another vapeshop. After all, I want you to
buy my stuff, not that of the competition

But there's lots of sites that provide all sorts of info/stuff for free - from cooking recipes to 'adult' sites. And they inject applets that track and rat on every mouseclick. Ain't so free after all then, cuz they making the money by selling your data. Had the same thing - was checking price comparison sites to get an idea of how much to set aside for a color laser printer. No spam, but sidebars and banners prominently peddling their range of ... you guessed it.
If the products costs nothing, then YOU are the product
Something like 'spybot search & destroy' ( donation ware ) or some other malware cleaner gets rid of the tracking crap.
Your e-mail addy is out in the 'open' by now .. so as said previously, flagging the sender sites as spam is pretty much all u can do - short of getting a new e-mail...
Most likley this, apart from using the firefox addons i've mentioned in my above post.
CCcleaner is a great program to clear out basic crap.
For malware Mbam is the way to go imo, i used to use Spybot search n destroy but i quite don't like it as much anymore. The immunitization it offers is quite nice though.
And for antivirus well that's another huge story everyone got their own preffs.

I like panda cloud, some other swears by other programs.
CCcleaner + privazer is both good programs to clear cookies/flash cookies and even registry if you would want that.
Granted with the firefox addons i've mentioned above, 99% of the crap will get blocked before it's even on your computer. Noscript for example is golden to avoid drive-bys/redirects.
Edit: Only downside to use no-script is that it takes time to get used to. Most basic functions on some pages will stop working, so you've to manually add the sites you deem are safe to allow, then you can allow temporarily or permanent. And you can pinpoint every script that is loaded aswell. (You'd be surpriced on how many scripts google is showing upon us, by even entering a simple site.)
Edit: just 2 simple examples...
(Some pages shows 100+ scripts this was just a simple wikia page, and the gamespot.)
Either way, both of these are golden.
Yet another edit:
Most of these are harmless but most of them are also just here to collect information about you.
Here's NT for example which i've approved. Scripts outlined in red:
So for anyone who does not use this, all scripts will be allowed per default. Which may or may not be harmful depending on what page you visit. But everything you do is collected and saved.
Also sorry for the huge post. ^^ Thought i should try to tell how google and other services are collecting the info to make commecrial tailored for you.