There are many ways to help a website or blog to get traffic. Most of the time you would need to spend some money but yet you still can get traffic for free. 
The most popular way to get traffic from Internet is from Google Adwords. Almost all business owners or affiliate marketers use Google Adwords for generating quality traffic to their websites. But trough Google Adwords you can't get traffic for free.
Researching Internet I found many ways to get traffic for free.

1. Search Engine Optimization
Search engine optimization is the best way to get traffic for free. There are many articles on the Internet, books, and companies that will help you to get traffic by optimizing your website for the search engines.
The best tools that will teach you how to get traffic for free is Google Sniper and Google Traffic Pump System. The both of them give you strong knowledge for Search Engine Optimization and the ways to get traffic from them.

2. Building Backlinks
Building backlinks is a part of search engine optimization and is the best thing you can do for your website to get traffic from the search engines for free. The backlinks, especially backlinks with high pr will change your competitiveness on Internet. If you get pr with 4 or 5 will list you always for your keywords in top 10 on Google. This listing will bring you thousands of targeted visitors to your website.

3. Participate in Social Networks
Social networks are driven force for your website that will make you famous and will bring you quality traffic to your niche. If you want to get traffic from Social Networks you should post always just quality information. Very helpful tip to get traffic from the social networks is to be opened for discussion with the people, to solve their problems according to your expertise etc. This will make you leader on the social networks what from other side will bring you visitors and maybe customers to your niche.

4. Build a list
Building a list of prospects is one of the quickest way to money on the Internet. Usually the prospects are interested in making money online and they sign up on your website or blog to learn from you. You should provide quality content to them to read or watch what will help you to build a relationship with them. If you earn them trust you will not just get traffic, you will get also customers.
How to build a list fast?
The best way to build a list fast is to provide a quality giveaway products. I highly recommend these products to be some top quality books or some videos that help the readers to solve their problem. Usually I use some books that I bought from ClickBank and they have reseller or giveaway rights. Never giveaway product that are copyright and you don't have permission to giveaway them. 
Great tip to help you attract more sign ups is if you use beautiful looking squeeze pages.
The best product I recommend that will build a list fast for you is "Super Sign-UP System". Super Sign-UP System provide you Giveaway Information Products with high quality, high converting squeeze page, confirmation page, download page, the One-Time-Offer Sales Page, the Master Resell Rights Download Page and the Quick Start Guide. All of these are great if your goal is to get traffic counted on hundred thousands visitors that can easily be converted on customers. 

5. Use Social Bookmarking Websites
Social Bookmarking websites are great for your traffic. You can get traffic by submitting your website to as maximum as possible social bookmarking websites. After building good reputation on them you will get traffic counted on millions for free. This traffic is free and quality. The most famous social bookmarking websites where you can get traffic are Digg and Delicious.

6. APSense - The Best Business Social Network

Participating in APSense can help you to get traffic for free. Writing Articles, Review Pages, participating in groups related with your website can help you to get traffic counted on thousands visitors per day. APSense allows you to create free campaigns that are also helpful for for you to get traffic. Upgrading you membership will allow you to post user ads that are shown always somebody visit your profile or your group. Imagine you create a group that will gather 1000 or 2000 members. You will not get traffic only, you will get followers, prospects and customers. 
If want to get traffic I highly recommend you this quality business networks.

7. Comment on blogs and websites
Commenting on blogs and websites is very important for promoting your website and building backlinks. When you comment always put your website link but be carefully to do not spam. If you spam you will not get traffic, you will be banned from the search engines. 
For this reason carefully how you want to get traffic. I recommend you to get traffic by using just the above tips.