I'm using PL/SQL Developer, which I think one of the best oracle database tools, it's lite and fast, I have one copy in my USB flash to allow me to use it in any pc(you just copy it from the program files folder and place it in the flash and it will work fine).
Also I bought OraDeveloper from DevArt three months ago, it's has some good features, but it's slower than PL/SQL Developer and require .Net framekwork. but the good thing that it has direct connection to Oracle, so you can use it from any PC without requiring Oracle client to be installed.
Another tools is EMS SQL Management Studio for Oracle, which looks nice, and have some nice features specially with import/export from other format.
http://sqlmanager.net/en/products/studio/oracle
and for free one you can use AnySQL Maestro, which has support for Oracle/MySql/Sql server and offer AnySql Maestro for free
http://www.sqlmaestro.com/