I can do a
select * from tab;
and get a list of tables (and apparently views) - are there similar views set up for other objects, such as sequences, etc?
Yes, there are (ALL_OBJECTS, ALL_TABLES, ALL_SEQUENCES, ...)
All of them are documented in the manual:
http://download.oracle.com/docs/cd/B19306_01/server.102/b14237/toc.htm