James,
Regarding studying SQL and PL/SQL, I recommend the Oracle documentation, which is available from:
http://tahiti.oracle.com There is the
SQL Reference and the
PL/SQL User's Guide and Reference There are technical forums available via the
OTN Web site.
By the way, Oracle have just released an
eXpress Edition (XE) which is free. Check out the
OTN Web site for more details.
Good Luck,
Avi.