Hm, the fastest way to generate traffic to your site is probably to buy traffic, but it's not very recommended to use "buy cheap traffic here" kind of sites since most of them just sends you automated/spider traffic that are worth nothing to you...
Most of the ways to instantly generate good and targeted traffic will cost you money, and the best ones out there IMO are Google Adwords and Yahoo Search Marketing.
I use Google Adwords myself with good success on a couple of sites, but it will cost you a bit so it's not recommended on sites you don't (plan to) make money from, and I also recommend to do some research on what keywords/phrases to use since it's very easy to blow your entire budget on unrelated clicks (I learned that the hard way myself in the beginning..
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Other ways could be to buy text links and/or banner ads on popular and related sites to yours.
That doesn't have to cost too much (normally from $20/month and up), and you can be lucky and get some real good traffic from those.
You could also post on forums with relevant content to your sites and link to your site from your signature.
But the most important (and best) way to generate traffic is of course to create quality content that people like and wants to link to and share with friends.
And you could try to submit your content/sites to Digg and similar sites since that may bring in some nice traffic if you're lucky.
And you of course should SEO your site so it ranks good in the search engines (but that will take some time..)