The book, "Inbound Marketing" by Brian Halligan and Dharmesh Shah of HubSpot. I hope that helps! It's a wonderful book with so much information!
I mainly use SEOmoz, Socialmediaexaminer, Hubspot, YouTube and of course Google Alerts to track subject information that I have an interest in.
One site I recommend is "DIY Marketers" (http://diymarketers.com/home/)--a good place to start for entrepreneurs. I've had engaging conversations with publisher Ivana Taylor and her energy, which is evident on the site, and content on the site (check out the Blog area) will empower you and spark your marketing initiatives.
If you are looking for the latest social media marketing tips, check out http://www.socialmediaexaminer.com/
Useful to businesses at varying levels.
It's a short book, and not really about social media per se, and that's Seth Godwin's Purple Cow. The reason is that for social media to be any good for you, you need to have a product or service worth talking about. Do your customers LOVE your product or service? If not, I'd start my research on how to build amazing service, high quality, or whatever your magic is to have your Purple Cow - something worth talking about.
Best of luck,
Internet Presence Management for Small Business
I also agree Hubspot rocks for marketing help. Also, check out socialmediaexaminer.com or learning.tigbee.com for some helpful articles as well specifically revolved around social media and inbound marketing.
The "Holy Grail" of marketing is Guerrilla Marketing by Jay Conrad Levinson. After reading that, you'll have a good overall picture of marketing options (mostly on the cheap). Other than that, it may depend what you're marketing. If they are personal services, such as coaching or speaking, Get Clients Now is an excellent, EASY to understand, EASY to implement system. I've heard Duct Tape Marketing also has that EASY/EASY formula for product-based companies.
Check out The Zen of Social Media Marketing by Shama Hyder Kabani
Kotler on Marketing. It's a detailed and self explanatory marketing book. I love it!
Checkout the articles & download the radio shows @ www.smartmarketingmoves.com