Oracle has release beta versions of the Express Edition (XE), a free (yes!) 10g release 2 database server with HTML_DB preinstalled. XE has some limitations over the real 10g database, but these are things like high-availability, advanced replication (basic is there), Java/JSP support, automatic storage management, etc. Things for the big players. XE is obviously targetted at developers and end-users currently looking at/using SQL Server Express.
OracleXE 10g limitations:
– it runs at the speed of a single CPU on multi-CPU machines
– the database cannot exceed 4GB
– only one installation and one instance (you can create more, but start only one) per machine
But: Oracle 10g XE is FREE!