Yahoo! indexes your site fast says many webmasters at a thread at Digital Point forum. When a webmaster asked if Yahoo! took long to index your site most answered affirmative.
Judging the tone of the webmasters Yahoo! takes a week or two's time to index your site however most of them have received good rankings with their site listed within page 1 itself.
One webmaster says Yahoo! "Took 2 of my sites forever but in the past 3 weeks they have been indexed on page 1 on many common keywords and im getting over 4k visits a day and growing." In total contrast another webmaster has a hilarious comparison saying, "It seems like it takes forever to get indexed. It's like watching water boil."
A great tip to get your site indexed fast was:
"If you make a post on Yahoo Answers and under the reference part place a link to your site it will be indexed in 2-3 days tops."