I have an MS Access (2000) database with linked tables to Oracle (9i).
 I want to be able to add records to the Oracle table in a form.  The
problem is the Oracle tables use Sequences to generate values for an
ID column.  What's the best way to get the sequence number or do the
insert.

It depends.  There might already be a trigger on the table that will
update that value for you.  In that case you don't do anything, just
insert a row without specifying the ID.  The trigger will fill it in
for you. Just try it.

Otherwise, you would have to know the name of the specific sequence
and in the insert call sequence_name.nextval. eg insert into mytable
(id,col1,col2) values(sequence_name.nextval,val1,val2);

There is no trigger.

I would like to add a record from an Access form--right now I am not
sending an Insert statement.

Access via the form sends an insert statement for you.(only mechanism
to add a row to the table)  What happens if you just try to add a
record via the Access form?  What exactly is the error message?  If
there isn't a trigger in Oracle on the table then the easiest way
would be to put one.  This would require the proper rights to do so,
knowledge of how to write a trigger (not particularily difficult), and
knowledge of what the sequence is called.  I fear that you are trying
to access something that perhaps you should not be via a mechanism
that your company doesn't support. (Access updating some application
table in Oracle)

How do you know there isn't a trigger?  You don't provide very much
detail.  Did you ask the DBA about the table?