This is a great page for finding about the new stuff in 2013:
Some of the key bits that i like are:
App Store – the whole world is becoming an ‘appy’place… and the new AppStore just brings SharePoint inline with modern thinking and modern approaches to product distribution. In the early stages there were a few ‘buggy’ apps that only really served as sales tools to get people interested in a new feature. Now there is a more robust selection of apps to choose from.
Cross Site Publishing – is a powerful new feature that provides the ability to publish and share libraries, across other site collections. I can already see plenty of uses for this in existing client projects that we are working on
Social Network – the whole product seems a lot more social networky and geared to following people and content. My first impressions are that most development has gone into this area.
Design manager – replaces SharePoint Designer for the branding of sites and provides an easier and more intutive interface to create and brand sites.
SkyDrive – provides offline storage which i think will prove to be a hit over time as SharePoint is used for ECM. I always found SharePoint Workspace a bit limiting and unstable so it’s great to have an alternative.
Elimination of Inplace Upgrade – In place upgrades are no longer supported, so the common approach will be the DB attach method.
Office Webapps – this is now a separate product in 2013 (no longer included with Enterprise).
FAST Search – is now included as part of 2013, improving the overall search experience.
Folders in Document Sets – The ability to now add folders to a document set is a useful improvement but as ever, my advice is to be cautious how you use folders. In certain situations they can prove to be very useful but it should be controlled and restricted so that there cannot be uncontrolled growth.
Shredded Storage – Versioning now only saves differences and not the full document. SharePoint 2013 automatically parses the document contents as it goes into the DB and checks for duplicate elements. This will massively reduce storage costs.
Friendlier Error Messages – at last… nuff said.
Live Document Preview – all the documents in a document library will have dots next to their names. If you click on those dots, you will get a fully navigable preview of the document in a nice-looking preview window. The preview window also allows you to zoom by double-clicking.
Site Notebook – Microsoft have included a shared notebook in each new team site. Everyone who has access to your site will be able to use the notebook. Click on the “notebook” link in the Quick Launch (the navigation menu on the left) to open it in the OneNote Web App.