There are many sites on the web that are excellent places to check out for Blender news, extensions, and services. This is a listing of some of those helpful sites.
Blender.today
Blender.today is a community-run website for Blender news. It works similar to sites like Reddit, where anyone can post a link or an article and the community up-votes or down-votes that post based on how interesting or relevant it is. The site is still new, but it's already proven itself to be a great place to go for the latest news as it pertains to Blender.
Pasteall.org
When getting help with your projects online, be it on sites like BlenderArtists.org or on IRC (Internet Relay Chat), it's often helpful to share files with others. Pasteall.org is a free site made by Blender users with that explicit purpose. You can upload images, code snippets, and even .blend files to share with others. Just upload your file and the site gives you a Web link that you can share with anyone else.
P3d.in
Sharing .blend files is great when you're sharing with other Blender users, but what if you want to share your 3D model with someone who doesn't use Blender? Sure, you could tell them to download and install Blender themselves (it's free, after all), but that might be more effort than they're willing to go through just to see what you've made. Fortunately, p3d.in helps fill that gap.
You can upload a static 3D scene and p3d.in displays that scene in 3D right in your web browser! No need for special downloads or anything. You share your scene and anyone can see it in its full 3D glory.
Sketchfab
Sketchfab offers features similar to p3d.in, but also has a few more additional features, including private viewing and integration with a few more programs and websites. It also shades models slightly differently, so you should both p3d.in and Sketchfab to see which suits your needs the best.
Sheep It Render Farm
Rendering your images and animations can commandeer your computer's processing power for long stretches of time. On a long, complex animation with a lot of detail, it can take days and weeks to render. This is why it's useful to have a render farm. A render farm combines the processing power of many computers to complete a render job, substantially reducing your overall render times.
Unfortunately, setting up a personal render farm can be very expensive. However, you don't have to spend that money. Sheep It is a community-based render farm. You can sign up and voluntarily offer extra processing power from their computers to help with rendering images. It basically allows you to use the entire Internet (well, at least the part that's signed on to Sheep It) as a giant render farm. It's an incredibly cool use of the Internet and a fantastic service.
Blendersupport.com
The Blender community is typically very, very good at providing feedback and support as you work your way through understanding how to use Blender. Sometimes, however, it's useful to have direct, hands-on assistance and training. The good folks over at BlenderSupport.com have exactly what you need. There is a cost for this service, but when you need just the exact right answer for your problem, it's certainly worth it.
Blender Network
As you continue working with Blender, you may start using it professionally (you know, to make money). Or perhaps you've gotten yourself good enough to be dangerous with Blender, but you need an expert to help on a specific part of your project. In either case, the Blender Network is the place to go.
As its name implies, the Blender Network a networking site for people who use Blender professionally. You can register yourself on the site to be listed among them, post and search for Blender-related jobs or, if you're looking for a Blender professional, you can search it for the exact person you need.
Blender Market
The Blender Market is a website set up by the good people at CG Cookie to allow Blender users to buy and sell assets for using in Blender. These assets could be models, materials, character rigs, and even extensive add-ons for Blender that dramatically increase Blender's capabilities. Through Blender Market you can purchase these assets or, if you've made something that you feel other people would find valuable, you can sell your own creations to the community.
Blender Cloud
As part of launching the Gooseberry open movie project, the Blender Foundation also launched the Blender Cloud. The Blender Cloud is the official “home base” for content from the Blender Foundation and the Blender Institute. All of the assets from each of the open movie projects can be found there, as well as any of the training material that's been sold in the Blender e-shop. And the site is still young.
In the future, you may be able to host your own collaborative projects there, and even use community-based render farming. There is a subscription cost for being part of the Blender Cloud, but for what's available (and what's to come), it's definitely worth it.
BlenderBasics.com
BlenderBasics.com is the author's website for Blender For Dummies. On this site are files and tutorials, all completely free for you. And if there are any additional files, tutorials or errata, BlenderBasics.com is the first place you should look.