Getting the word out to people about your company, hobby, organization, or interests is very important and email is a great way to do that. Unfortunately, spammers also know this and constantly try to abuse any system created for easy communication. Newsletter emails can be done in more compliant ways to assure much higher delivery rates as well as custom styles to separate yours from the rest. Using a professional service is highly recommended for newsletters over email.
Email, the center of so much communication for any individual or company. Protecting email communication is a most definite priority for any website owner. Where your email is hosted, what system it's using, and how secure it is are all concerns that should be addressed.
Online shopping is incredibly common now. Every store has a website selling its products. eCommerce is something that requires careful consideration before just putting things up for sale and assuming payment stuff will just work out. Quite a bit goes into how an eCommerce system works and there are many requirements that must be met to assure that everything operates as intended.
Social sites and social features are incredibly huge on the web right now. While it seems like every feature exists, the right combination and branding may not be there for your community, club, organization, or company. There are growing options for software that will allow you to run your own community, no matter how large, and will provide tons of features to keep your users interested.
Project Management remains in it's own category of systems and if you're looking for any type of tracking employee activity, client requests, tasks, etc., a project management system really needs to be used from the start.
Content Management is a term with a very broad definition, largely because the word "content" can refer to nearly anything that can be posted on the web; papers, videos, photos, PDFs, and many others. The defining factor of what makes a system a content management system versus another type is what it does with the content.