Ok, so 11g has been out some time but I've been to busy to really dig in to it until now. 11g is probably the first release that doesn't really many new features; no, before you send me angry e-mails hear me out :)
Take a look at the new features list. What do most of these features do? Easy, they just make the most out of the fairly old but totally outstanding REDO and UNDO management in Oracle. Why not use what we already got? Ok, some things are totally new features like the improved partitioning and new data types for the medical and life-sciences industry.
Partitioning and compression
The coolest things in 11g is probably the VLDB features for partitioning and compressions, can really reduce storage costs (at the same time as storage costs are plummeting with the competition from iSCSI). It is now possible to create "automatic" partitions, i.e. instead of adding a partition every month with DDL when doing a bulk load Oracle can automatically partition the table as per predefined rules. Pretty cool and saves a lot of time.
Another pretty cool feature, at least for me as I'm using a lot of Netapp NFS storage, is the Direct NFS client in Oracle (Linux). Switch to the direct NFS lib and Oracle will do NFS ops outside the Linux kernel, which removes the NFS caching layer and kernel block device mapping etc. Gives a quite massive performance increase on some workloads. This is what I'm playing most with at the moment.
Lots of new cool stuff for Data Guard. Most significantly is probably the fact that you can have an open standby, available for real-time queries such as reporting applications and other read only operations. In fact, you can even open a Data Guard instance in read-write mode and mess about with it and later just flashback to a SCN where the db was in sync with the Data Guard master db and just roll forward to the current SCN using the normal FAL services. How sweet isn't that for DR testing and schema change testing. DR testing during live operations, that's a couple of late nights saved.
Other new data guard features include redo shipping compression, the normal improvements to the DG broker, sqlplus manageability etc.
Another thing that is really useful for deployment testing and change control is the database replay feature, one can "record" all transactions over a period of time and replay them after a change has happened to ensure performance and functionality has not degraded.
Improved ASM features.
You can now bring online a replaced drive and new writes will go directly to the drive while Oracle sync data from a redundant mirror in the background. Reduces resync time quite a fair bit.
Couple of improvements to plsql;
Use of sequences in declares.
Real compound triggers.
New data types
Not really my thing but probably useful for a lot of people.
Spatial and multimedia support for medical imaging, life-sciences and other fairly odd things. :) Docs here.
A couple of minor things have changed as well, the alert log lives in a new place (with it's buddies in the new diag system), the logging levels in the alert log can now be adjusted as well (got a blog entry about that in a couple of days).
Lots of fun things to play with and to blog about.
Ah, almost forgot. Larry pulled a version hack on us again. As some of you may now there was never an Oracle Version 1 release, the first version was called 2 since Larry Ellison didn't think anyone would buy version 1. The first (public) 11g release is 188.8.131.52