The bane of digital photography (in my perception) is dust/dirt on the
sensor.  Had I known about this I would still be waiting to make the
switch from film.  But now I just can't go back to hauling a roll out
every 24 shots, threading another one in... AARGH!

I think the key to solving most problems is understanding them - the
concepts involved and the forces at work - etc.  But in this case I
have been able to find nothing that even begins to explain why dust is
attracted to the sensor.  Some say it's due to static charge but the
battery packs a whopping 7.2 volts - not a lot of charge, there!

Eleven days ago I upgraded from a 20d to a 30d (with a "IS" lens,
which still gives me the willies...).  I looked and looked but found
no camera with the ability to change lenses AND enough pixels to do
the job that did not have this problem.  Sigma makes a camera (which
is rated as mediocre, in every respect save its sensor) in which the
filter is a fair distance out in front of the sensor, creating a
situation wherein dust is not in focus and does not show.  Sadly, that
camera lacks sufficient resolution to be used professionally.

I thought the 30d would have to be better.  WRONG.  After only 11 days
and about 250 shots the dist is back... not bad enough to panic me
yet, but back.  It makes you wonder if this is something designed to
make money after the sale...

So, would everyone please be kind enough to add what you know about
the basis of the problem; about how you clean your sensor safely,
reliably and, above all, at a reasonable cost - pretty well anything
that will help to expose, define and then solve this problem not only
for myself, but for all?

Before I go I suppose a few words, in the way of a review of the 30d
(so far) would be in order.  Some, even most say that the differences
between the 20d and the 30d are not enough to warrant the money
expended, in order to upgrade.  Myself, I could not disagree more.

My 20d was one of the very first two to appear here, in my little hick
town in the mid-west.  I got it the day before they were officially
released.  Maybe that is why that cam was soooooooooo funky.

The viewfinder - OH MY GOD!  So grainy I was completely unable to
focus, manually.  I had to remove it and clean it hard several times
(with acetone!) in order to get whatever miserable coating that was
the source of the grain off of it.  I'm not a camera mechanic and that
stuff makes me nervous... and afterwards the viewfinder was still bad,
but usable.

None of my other complaints about the 20d are that strong but, taken
together, they made for a dubious and uncertain relationship with the
cam.  I never did trust it.  The dust magnet thing certainly did not
help!

The 30d says to me:  I'M READY.  The years in between must have
provided papa-son Canon with a liberal dose of feedback from 20d
users.  The viewfinder does what it should - I can focus manually with
relative ease (but no diopter).  The thing weighs a ton, thanks to the
28-135 IS lens which is crystal clear, relatively sharp and seems to
do what is says it will do.  The camera is intuitive - the ergs
improved, by light-years.  It's not slick, like a Nikon.  I don't
really like that.  What I do like is the cam being out ahead of me,
waiting for me to do my part and responding, instantly.  I think we
are on our way to being joined, at the eyeball .)

One problem, remains.  Maybe this will be the message that begins the
process of solving it... ???