Well dood...there are lotta softwares/programs on which u can apply DBMS. Plus u can make ur own DBMS like in VB etc. There are new softwares that are created daily. Microsoft access also provides u with DBMS!
The few top ones in which u test DBMS and learn, and which are used commercially are : ORACLE,postgreSQL,MySQL,Micrsoft SQL server !
Outta these ORACLE is used most commercially. PostgreSQL has all the features that are implemented in DBMS standard. MySQL is the fastest in terms of processing etc.
If u wanna learn all about DBMS + compare the above four....IM me ur email and I'll give u the name of the ebook to it!