There are tons of ways to gather links in a short time. I don't think I can list program names here. However, if this is a site you care about and want to prolong the longevity of, I wouldn't be looking at building links fast, but rather building links of quality. In the long run, it will be a better gameplan. IMHO.
Create awesome content that everyone wants to link to--that just happens to get mentioned all over the news.
Or create controversial content. Personally, I would rather do the former.
I agree with chrisnrae. A good link campaign needs careful selection of links. And good sites link back to you if you are linkworthy.
So spend time on developing good content and people would link back to you and if you are asking for links, do that manually. Time and patience.
Thank you for your suggestion and assistance.
In fact, many company sell their SEO program software or solutions to build up the traffic in short period.
So I need clear to know how can they do that.
Probably by adding a link to your site across a network of sites they own, or across their network of client sites (with or without their knowledge).
So, unless you have a network of sites and the knowledge on interlinking them and understand the risks of doing it less than well - you won't be able to duplicate what those SEO companies are offering on your own.
And I'm not even saying you would want to. Again, a lot of different factors and risks at play.
"build up the traffic"
Also, building up traffic and building up links are two different things. Some SEO's have generic sites that can funnel traffic to any client they choose.
chrisnrae is right. You put yourself at the mercy of another company's methods, possible misuse of software, etc.
Here's a thread about some of the perils associated with outsourcing [webmasterworld.com].
there's no substitute for sending a real letter addressed to a specific person. sure, takes a bit more effort. But everytime I get a solicit from someone who obviously doesn't know a thing about my site or why it might be good for my users to see their link, i dump it immediately. And, more to the point of this thread, I find that I get much more response if I send a letter such as this.