DEFAULT confusion

Hello postgresql'ers (how do you pronounce that?).

Suppose i have the following sequence, table and index:

CREATE SEQUENCE stuff_seq;
CREATE TABLE stuff (
id INTEGER DEFAULT NEXTVAL('stuff_seq') NOT NULL,
name TEXT,
number INTEGER
);
CREATE UNIQUE INDEX stuff_id ON tabel(id);

Then to properly insert rows i have to

INSERT INTO tabel VALUES (NEXTVAL('tabel_seq'), "sometext", 123);

I can't just
INSERT INTO tabel VALUES (NULL, "something", 123);

Then what is the point of the DEFAULT clause? In other words: How do I
get away with not specifying anything for id? And how (if
possible/recommendable) do I force the id value to be nothing but
NEXTVAL('stuff_seq'), ie. not just an arbitrary number?

In short I want to emulate MySQL's way of doing
CREATE TABLE(
id INT NOT NULL AUTO_INCREMENT,
name TEXT,
int INT,
UNIQUE(id)
);

I hope I made myself sufficiently clear.

Thank you for your time.

PS.
Where can I get more information about the REFERENCES keyword and when
will it be fully working in Postgres?
PPS.
Are there any books out there that cover Postgresql?
--
Hroi Sigurdsson
hroi(at)ninja(dot)dk