Search engine optimisation as you may know is the process of getting a website on to the front page of a search engine. Organic SEO is the process of getting a website on to the front page of Google (or Yahoo, MSN etc) naturally as opposed to Pay Per Click, or sponsored listings.
The benefits of organic SEO is that once a website reaches the front page for its given keyword/phrase then it tends to stay there, and is considered to be there on merit. The process will take longer than the instant quick fix of a PPC campaign, but saves money in the long run as it is not limited to a given set of page views.
We've put together various packages for an organic SEO campaign for our clients. Each website and industry is different with regards to search engine optimisation, and different tactics are needed. For as little as £100 per month over three months your website may reach the front page and stay there for over a year.