Thanks for the great ideas, folks. Please keep 'em coming!
If you are getting the two lens kit, I would hold off on other
lenses until you see what your shooting style evolves into.
Besides lens lust seems to be a never ending drain on expenses.
The essentials IMHO are listed in order or importance to me:
At least a gig memory card (or 2 512MB cards, etc.). I don't know
the sizes of files that the E300 puts out, but on my E1, I get ~ 67
files when I use RAW+JPEG and ~ 250 files with JPEG. Figure
somewhat less for the E300 since it has a higher resolution.
Multi-coated UV filter for your lenses (since the two lenses in the
kit have the same filter diameter, it makes it simple). You don't
want to skimp and go with the really cheap non-coated stuff, since
it will affect all pictures you take. There are other people who
say skip the UV filter all together, and this is a never ending
debate. Hoya SMC and B+W tend to be the quality names you see. I
like
http://www.2filter.com for filter deals.
A bag to carry your gear. Lots of different options -- I tend to
recomend taking all of your gear to the store and seeing what fits.
FWIW, I have a Lowepro Nova 1 bag that is just perfect for carrying
the E1 and my 3 lenses, or the E1, 2 lenses and a flash, though it
is rather cramped if I try to carry anything else.
A wrist strap. I hate neck straps, and find a wrist strap gives
you adequate protection against camera drops. Do make sure that
the strap is strong enough to hold the camera.
Polarizing filter to make for better outdoors pictures in good
light. Here unfortunately budget raises its head. The really good
multi-coated polarizers (B+W, Hoya SMC) will set you back around
$100, and the non-coated Sunpaks are much cheaper, but can give
rise to flare more often. Depending on your shooting style, it
might make sense to go with a Sunpak filter to start out, and if
you find yourself using it quite a bit, think about upgrading.
When I got my E1, I got one of the slim filters without front
threads, and I find it hard to turn, and I couldn't use 3rd party
lens hoods, so I wish I had gone for a normal sized filter with
front threads.
I'm a big external flash believer. If budget is tight go for a
generic auto flash (though there is a learning curve involved if
you've never used auto flash before) like Vivitar 283, Vivitar
285HV, Sunpak 383 -- you want a flash that tilts and hopefully one
that swivels as well. If you have a little bit more money go for
the FL-36, and if you are going to use the flash quite extensively,
go for the FL-50. Skip the FL-20 (too limited), and FL-40 (doesn't
work on E-300).
A second battery is nice, but it is perhaps not strictly needed
until you get more memory and plan to take more pictures between
downloads and recharging. I don't know if I've ever run down my
battery since I got the camera in December.
If you go the tripod route, go to the store and try the camera on
the tripods. A tripod that is shakey and can't hold the weight
kind of misses the point of using a tripod in the first place (I
suspect the $20 Walmart specials are too light for the E300).
If you go the tripod route, consider getting a RM-1 infrared
controller that will allow you to fire off the shutter without
touching the camera (and causing vibrations for long shots).
Unfortunately, Olympus no longer adds this to the standard camera
package (I have two of them from previous Olympus cameras), but
they are fairly cheap. Note, on the E300, a cable release (RM-CB1)
requires the use of the vertical grip and will set you back quite a
bit (both are overpriced IMHO), so I would skip unless you really
need the functionality for bulb shots.