A wonderful list of marketing ideas to promote your business. Am bookmarking this page as a reference, as I already see there are a lot of links I want to read further. Thanks for putting this together for us.
My favorite methods are article marketing and blogging, they really help bring a significant traffic to my site, I also use Facebook and Twitter but I rarely optimize it since I don't have that much time.
How To Sell yourself to others is first to sell the others to yourself
I have read this whole stuff and the thing is that I want to say you that include any URL, such as business cards, stationery, etc. This is also a good source of business marketing. Good places to leave business cards in shops, banks, etc.
Press Release, free classified ads on trusted sites, free directory listings on reliable sites like Demoz, Yahoo Directory (still has free sections for submission), Yellow Pages. Last but not the least ask your clients/customers to write some reviews about you & submit it on review sites. I've used these tricks and successful.
Online directories also have a place in promoting your business. Select your keywords carefully when putting your directory listing together as it can have an effect on where your listing appears on Google if the directory site itself has good search engine optimisation.