This was one of my early posts and it seems the instructions work the same for the new October 2010 early release version of SQL Developer. (it was pretty straight forward anyway).
Grab the SQL Developer 3.0 RPM from Oracle (registration required):
You’ll need the Alien package to convert the SQL Developer .rpm to a .deb package and the Linux Standard Base (lsb) package and a Java Runtime in order to run the application.
$ sudo apt-get install lsb java-6-jre alien
Build the .deb package using alien:
$ sudo alien --scripts sqldeveloper-3.0.02.37-1.noarch.rpm
I did get one error doing the build but it completed successfully anyway:
error: incorrect format: unknown tag
Install the .deb package:
sudo dpkg -i sqldeveloper_3.0.02.37-2_all.deb
And run the application for the first time, it should ask you where your JRE is, mine was in
SQL Developer should now be installed in the Applications menu under Programing.