Last year Scott Spendolini gave our company an excellent 3 day training session on APEX. He also showed us a very nifty function (new in 10g I think) to help not having to escape single quotes when defining strings. This is not APEX specific, however it will help you if you ever have to write a block of PL/SQL to return an SQL statement for reports.

Instead of writing out a long description here's an example:

DECLARE
  v_sql VARCHAR2 (255);
  v_result VARCHAR2 (255);
BEGIN
  v_sql := 'select ''hello'' into :a from dual';

  EXECUTE IMMEDIATE v_sql
               INTO v_result;
  DBMS_OUTPUT.put_line (v_result);
END;

Notice how I had to put 2 single quotes around "Hello" to escape the single quote characters?

Now using the q function I don't need to do that:

DECLARE
  v_sql VARCHAR2 (255);
  v_result varchar2(255);
BEGIN
  v_sql := q'!select 'hello' into :a from dual !';

  EXECUTE IMMEDIATE v_sql
               INTO v_result;
  DBMS_OUTPUT.put_line (v_result);
END;

Notice now how "Hello" is wrapped as it would appear if it were not in variable definition function?

This can save you a lot of time by avoiding having to escape single quotes in strings!

Update:  q Function Inside a q Function