Oracle Database 11g Express Edition (Oracle Database XE) is a free version of the world's most capable relational database. Oracle Database XE is easy to install, easy to manage, and easy to develop with. With Oracle Database XE, you use an intuitive, browser-based interface to administer the database, create tables, views, and other database objects, import, export, and view table data, run queries and SQL scripts, and generate reports.
This version fixes the bugs 10 XE has that were fixed in the standard version and has some new features but doesn't have some cool new features of 11g like PL/SQL Function Result Cache :-(: see Feature availability
Documentation can be found here
Requirements: approximated 0.5 Gb for software installation
Limits: maximum of 11 Gb for user data (it was only 4Gb in the 10g version!). Uses only the equivalent to only one CPU and only 1 Gb RAM.
It ships with APEX installed. update: Attention: According to this posts it ships with a weak default password for APEX_040000 user and APEX Patch 4.0.2 is missing.
Update 26-July: the version I download yesterday for Windows has already APEX Patch 4.0.2 and the user APEX_040000 is locked.
Notice: this version doesn't work with SQL Developer below 3.0 versions. A bug that is promised to be fixed in the final version.
I hope the final version will see the light very soon (maybe for Oracle World?)