1.Classified Ads Marketing is known to many but not as mobile marketing,there are classifieds that has mobile version like craigslist.its one way to generate traffic to your mobile websites.
2.Forum Posting,Some popular forums has its mobile version and can be access from mobile.
3.Social Medias are still powerful media to use for websites likewise for mobile version of it.
4.Google Places and Rating Sites can cause website to generate good reputation hence when people tend visit your website on mobile phones the mobile website generate traffic.
5.On page SEO on mobile website can stand on its own hence generate good ranking on search engine on mobiles.
6.SMS, you can send SMS through free software or web base tools
7.Offline Marketing, in offline marketing you can use QR codes where people can scan them that will lead to your website
8.Mobile Application, where people download and just visit your website through it.
Marketing your regular size website would be the best option and having your regular visitor access your on mobile, that's why building reputation is important.
That's the reason why mobile SEO could be more expensive because its difficult to do.