google: http://www.google.com/intl/zh-CN/add_url.html
baidu: http://www.baidu.com/search/url_submit.html
sougou/souhu: http://db.sohu.com/regurl/regform.asp
yahoo: http://search.help.cn.yahoo.com/h4_4.html
中搜: http://ads.zhongsou.com/register/page.jsp