I'll pick article submission from this one at first place as I have had good results with it as compared to other methods mentioned here. Forum participation usually needs outsourcing if the time limit is less which is not so with article submissions.
Create a useful tool that people can use for free and will appeal to many. Get the word out and you will see thousands of natural backlinks to your valuable service. If you want alot of backlinks in one day post a bunch of real comments on blogs related to your website.
I find that forum posting is the most effective method for me. That link with the top 100 dofollow forums is a good start!
If I may give you a tip. If your websites have a unique spin I would definitly choose for a proffesional written and distributed press release. It's a snowball and contain almost no work from your side!
I have a question for those of you who say forum posting helps in link building. How much more valuable is 100 links from this forum vs. one link. One a site has linkd to my site is there much value in multiple links? Ned Carey
Most efficient are probably commenting others people blog that have a high PR The other method that work best is to post quality post in forums and place your link in your signature.
No. Once you have a link here, it counts the same. Brad Callen of SEO Elite expounds on this in his training materials. He says it's important that your links come from different IPs.
Quite frankly, they are not quality links. And if the thread you are in is not relevant to your signature link, then your link is worth even less. Forums used to be a good bastion for developing hundreds of links in a short period of time, but Google has shut the door on this method. If you want to know the secret of getting quality inbound links, then maybe some words of advice from Matt Cutts will offer a few clues: SEO Advice: Getting Links
a Fast way that I found to get links to my site is to place my link in the header of a site that use only one header for 100's of pages. I have a Arcade site that Flouts around the web and dicided to put a link in "powered by" and sites name I waned back links on and after the site was crawled, I went to Google Tools and place there meta tag in my site. To my suprise 136 back links. I hope it gives you some ideas.