The backend of a Drupal site basically is used by two very different groups of people. First, the developers who build the site and do a lot of stuff usually called "administration" of the site. On the other end, there are the editors, who mainly create and edit content. On content heavy sites the editors probably spent a lot of time using the backend to do their work - and at the same time they probably are not computer experts.
Drupal provides a very basic interface for editors, which is fine for small sites, or sites with relatively static content, but for some sites it would be nice to provide some extended interfaces for creating and editing content. Luckily this is very easy by using standard Drupal site building tools in just a short time. Taking in consideration the very special needs of each website and team of editors, the developers can easily build custom user interfaces to make content editing fun!
Create custom admin menus per user role
The editors probably have just a handful of tasks that they need to do very often. Create custom menus, to make those pages easy to reach. Using the Drupal core shortcut module, editors can even create a set of up to 7 links to pages they consider important. Another module which can help you is quickbar.
Create custom admin pages and content listings
Using and Views Bulk Operations you can provide custom content listings, probably using exposed filters, which show the needed bits of each content type and provide some ways to execute common actions like publishing content, etc.
Another neat Views based module to improve the editor experience is draggableviews. If you have any view on the frontend where you would like to control the order of items by hand, you could setup a backend view with draggable views which allows you to sort the view by drag and drop and save the order.
Structure the node edit forms
This one is super easy as there is one module which allows you do a lot of structural improvements on node edit forms: Field Group. It allows to create different types of field-groups like accordions, tabs and so on.
If you need to have fields which are only visible if a certain option was chosen, you can use Conditional Fields module (Hint: you might want checkout this sandbox module for D7 as well: http://drupal.org/sandbox/peem/1073388).
If you want to hide some fields for some user roles, check out this module Field Permission (Note: Be prepared to have lot more permissions on the permissions page ;)
A new thing in Drupal 7 are "Contextual links". Use them, which means take care not to strip them off your in your custom theme. And, you can also use them within views, yey! (see this issue for the new feature in Views 7.3.3: http://drupal.org/node/1019486)
More reading and stuff about this topic
This topic is currently discussed a lot, and Dries even has the plan to setup a Drupal 7 distribution (using make files) which collects the best practices of improved editor experience (See http://drupal.org/project/phoenix).
More blog posts and presentations: