Communities can make a big difference for an author just starting out in finding their way, meeting likeminded people, and getting useful guidance. You should join communities even before you are ready to publish a book, because they have a lot to teach. Some of them cost money to be a member, but others are completely free.
Here are a couple of great communities that can really help for a struggling indie author or someone just beginning their career. I've learned countless useful things from the following groups, and I'm sure that with a little bit of effort you will too!
IBPA is great and has a lot of really cool services and promotional options available for authors, but it can get extremely expensive very fast. I wouldn't sign up here unless you are actively trying to take your career to the next level and want help with purchasing expensive promotions that are shared with other authors.
They offer some great things. There are classes you can sign up for, shared promotions on places that normally cost thousands and thousands of dollars to be listed on, and a lot of other cool things that you couldn't find on your own. The people who run the website are great, and there is a strong sense of shared community throughout.
I have only done a handful of classes, but it seems they try very hard to offer unique and cheap content to their members that will actually help drive sales, which is something I think is great.
I have been a member for just under two years, and I still haven't managed to find my way through even half o the free content they give to authors, including articles, videos, and more. They also offer membership discounts for a lot of different services, but in general I haven't found these to be tremendously worthwhile. Most places already offer discounts outside of IBPA, and occasionally those discounts are better than the ones offered with the discount system.
Probably the strongest part of working with IBPA is the group promotions that they offer. They set up monthly and annual advertising options where you can pay a little bit of money to have your book listed in a mass catalog sent to booksellers, libraries, and a multitude of other locations that would be willing to sell your title. I've participated in a few, and even when things went poorly (such as when they accidentally printed the wrong information on one of my ads) they were a pleasure to work with and quickly corrected the issue.
The problem you'll face is that their outreach is almost exclusively paperback, not EBook. If your goal is to build up your digital audience, then this will serve almost no purpose.
You can easily spend a lot of money with IBPA and get very minimal results, but you could also tap into an entirely new market that might create a long-term revenue stream. It is more of a service organization than a community, and in general paying the entry fee is only the foot in the door before you have to bust open your wallet for more money. But, if you are trying to push into the paperback market, this is a great place to start!
This is one of the sites that is hard to beat for authors. It has a great community of people who are constantly looking out for each other and helping bring everyone up. I've learned more from participating on KBoards than anywhere else.
There are a lot of people using this website, and some of them are making a lot of money using advertising. Many are friendly, some are competitive, and the important thing to note is that there are smaller sub-communities hidden here for every possible niche. One great thing about this compared to some places is that there are a lot more readers here supporting authors than at other places (for example, on WriteOn it's all for workshopping, so basically everyone there is an author).
Basically, you post a story and then you promote it. It is as simple as that. People can post comments and give you feedback about it, but for actually setting up an account all you need to do is input a little bit of information, post your content and a cover, and let things go from there.
This is, hands down, the most important audience you'll ever join as an indie author. It is full of everyone you could imagine, from veterans making six figures to newbies making three.
In general, everyone is friendly and welcoming and always willing to help. Whether you're looking for information about a book you're currently writing or want to find out about latest trends, this is the place for you. The conversations can occasionally turn hostile, but the community organizers are always ready to stop in and make sure things stay on track.
There is also an incredible community of kindle scout authors here who are constantly running campaigns. There is an ongoing list of nominations to cross-promote one another and a wealth of information. All in all, if you aren't already using kboards, then you have to check it out.