I have to say article marketing since you have to write an original article with a link to your page about a topic related to your site and submit it to Ezinearticles, squidoo, ehow, hubpages, and other article sites.
Online video marketing can also be very labour intensive since you have to make a video which is informative, and entertaining, and post a link in the video or the sidebar.
making a video (ensuring that the music and video players together well, ect.) finding good decent places to ad and making up articles that sound pleasing to all.
Advertising anything on the net, is not as easy as it may sound.
Guest blogging inexchange for a link back to a website is also hard since the quality blogs with lots of traffic don't let most people guest blog for them. You sometimes really have to make a pitch like the late Billy Mayes for them tolet you guest blog on their site inexchange for a link.
