Online marketing can be done by following ways.
Banner advertising : just put a banner in major portals and get your maximum traffic this a way to generate awareness about your newly or existing sites. It will be easy for you if you have a banner with popular portals such as yahoo, rediff or indiatimes.
Viral Marketing: This could be a way to generate awareness about your campaign or newly launched product. it could be done by video, games or sms for reaching your consumers.
Seach engine marketing: This could be done by seach engine optimization with yahoo, google, msn, altavista. select your keywords and get in touch with your consumers. or you can display text based advertising as sponsers in search engine.
Affiliate marketing: As per my earlier post this is could be a best method for online marketing. you can generate online sales by the way of this method.
Email Marketing: Get the database and mailed them your offers. when people will see your mails they will go for online purchase.