I finally got the RSS working. Now, you can add this blog to your my.yahoo.com by simply click the “+ My Yahoo!” button on the upper-right corner of this site.
The key is to success is to ping Yahoo about your site changes. This can be easily done in WordPress by adding “http://api.my.yahoo.com” to the write options->update service. Initially I didn’t put “http” there and it didn’t work. Now you can even go to Yahoo page->Add Content and search for this site. It will popup in search if you put in the key words Technology, Manage, and Toys.