Time for the weekly (sort of) Lost summary of what I found after nitpicking the episode, snooping on forums as well as blogs.

Spoilers are obviously present , so watch first, read later, or read one of the old summaries.

Episode 10 - the 23rd psalm

First of all, let me summarize this episode's character development:
Character development, measures in amounts of awesome

Eko's stick

First of all, let's take a look at the inscriptions of Eko's 'Jesus stick':

Jesus stick

CORINTHIANS
"HATETH"
TITUS:3
REVELATIONS:#
23 PSALM
PSALM 144

I'm not very good with interpretations, but Psalm 144 seems to be a generic prayer, a part of Titus:3 could relate to this episode:

Warn a divisive person once, and then warn him a second time. After that, have nothing to do with him. You may be sure that such a man is warped and sinful; he is self-condemned.

That's what Eko's brother did, and died believing that his brother could not be helped after the second warning, but I guess after bing kicked out by his friends he became religious again.

The monster

Yes, you did see faces and stuff in the smoke, with some enhancements, most of the images became pretty clear:

Eko's brother's church
Eko's brother's church

Young Eko
Young Eko

Eko's brother
Eko's brother

The old man from the childhood flashback
The old man from the childhood flashback

Screamhing people left behind
Screamhing people left behind

A crucifix
A crucifix

Old woman
Old woman

A man, upside down
A man, upside down

Unsure
Unsure, young Eko's brother screaming?

I see two possible solutions: it's recording Eko's memories, or it's displaying it, which means that the island is all-knowing. My bet is on the first theory. One important question is also if the monster is there to be studied by Dharma, or if it's implemented by Dharma. Is it controlled of self-conscious?

Random stuff

Just for the record, the code for the weapons locker was 25, 29. I wouldn't expect the lost numbers to turn up there anyway, it'd be my first guess if I was breaking in.

Charlie was trying to sing The Kinks - He's Evil, it's a pretty good song, get it :)

The registry number for the plane was 5Z-GWN6, apparently they didn't bother faking one, as this one's registered in Hawaii, there Lost is shot (check at FAA).