OK this is my little SEO boosting tactic which I will share with you.
1) Open Yahoo answers account, you can adjust your profile, but it is not crucial(will get you more credibility)
2) Open another Yahoo answers account(you can open few, just watch for your IP)
3) Store your user name and passwords, roboform is great tool
4) Log in with your 1st. user name
5) Create question, but be sure that you have included your keyword in question title.
6) Log in with your second account, answer question and put linkback to your website in the answer, don't make it like a spam
6) Now log in to your 1st. account and choose best answer you just created
7) Use main social bookmarking sites to bookmark your question url
8) repeat steps from 4-7
Remember if you need very big number of questions and answers you can always outsource your work.