One of my successful tests and I wanted to share with you. I know many of the webmasters already know the practical value of .edu and .gov links, even if the link page doesn't have any PR. I tested them at 3 of my sites.
Test 1. only some .edu links (50+, NO PR but do-follow links)
Test 2. only 2-3 .gov link (NO PR but do-follow)
Test 3. Article marketing (7-10 articles per month; syndicated to top 15 article directories) + .edu links + .gov links
Test 1 - Good improvements (Rankings improved by 17 positions; Jumped to page 7 from page 9) The program ran for 25 days and results started showing up after 15th day or so.. stayed for 1 month .. till date
Test 2 - Little improvement but I'm hoping some good. it was difficult to attain many .gov links.
Test 3 - Fantastic improvements (On page 2 bottom from Page 7). The program ran for 25 days and results started showing up after we finished. But very nice improvements. Now to move up to page 1, I just need some article marketing and some contextual links.
Just to inform, I ran these tests on average competitive keywords (seo copywriting services) to super competitive keywords (diet pills).
So, I'd say a combo of .edu links, .gov links and article marketing gives amazing results and needless to say; stable too. This is one of the best link building combos that works really well..