"Must Have" Olympus OM lenses?

You've got the wide to normal range covered. Why not look for the 100mm f2 or the 180mm f2.8? I would not mind either one of those to use with my Olympus DSLR.

In your shoes, I would look for an 85/2.0 - a great little lens - pretty fast with a very pleasing perspective or, if you really feel like spending some dough, the 90/2.0 macro. After that, the 180/2.8 or the 200/4.0 - I have the 200, which is very sharp and compact. With the 180, of course, you'll have a lot of weight hanging off the front of the camera, but also sharp as all get out. Also, see if you can track down one of the small screw on handgrips for the OM-4 - they're pretty rare over here in the US (based on what people are asking for them when they come up on the auction site) but I think it really improves the handling of the OM-4.

FWIW, here's some comprehensive info on Olympus lenses:
(link)

I also think 100/2.0 and fast macros (90/2.0 or 50/2.0) would be interesting. Fast wideangles like 21/2.0 and 28/2.0 would be nice, too. The problem is that all of them are extremely rare even here in Tokyo.

If you are interested in some closeup work, Zuiko MC 1:1 Macro 80/4.0 or Zuiko Auto Macro 135/4.5 with Auto Tube 65-116mm would be interesting, too. They are fairly easy to find.

Good luck!

Jeff, have you thought about zoom lenses? I too have the OM lenses of yesteryear and they also do quite well for the E-3 and E-30, especially the 55mm f1.2 --- great portrait lens as it is equivalent to a 110mm on any of the E-series DSLRs.
Depending upon the type of photography you often shoot or consider shooting, you may want to look into the telephoto and zoom lenses. I used to shoot with the Vivitar Series 1, 28-105mm, f/2.8 as a primary lens because it covered about 90% of my assignments.

You have the wide angle and standard angle range pretty much covered.

I would recommend a good portrait lens, I particularly like the Zuiko 100/2.8 as it's great value for money, otherwise the 85/2 or 100/2 or 90/2 macro

I would consider a macro, I use the 50/3.5, you can also get the 50/2 or 90/2

I would consider something in the 180-200mm range. so depending on your budget either a 180/2.8 or 200/4

Accessory wise... maybe a 2-13 focusing screen? flash? spare body?

Second that for the grip and the 2-series screen. They make a substantial difference in the OM4Ti.
If you can pick up the 40/2 or the 21/3.5 at a decent price I'd jump on those as well.

I use a 55 1.2 on my Canon digital body (as well as my OM1), and i am always coveting the 40/2 and the 85/2, both of which are in stock at a used shop right now in my neck of the woods (so sad, no pocket change right now). i agree with Greg above though that your bag is lacking the longer lengths.

Of the less exotic but still very good Zuikos I can recommend the 50/3.5 macro and the 100/2.8. The 50 is a floating element design and is extremely sharp at any distance. The 100 is compact and excellent for portraits.

Thanks for the advice. I ended up finding a mint 90mm 2.0 macro for a pretty good price. I looked for the grip, but couldn't find one (that wasn't already attached to a camera). I found lots of things like macro accessories and lenses, a couple shift lenses, and one shop had half a dozen old M1's sitting on a shelf.
I'll try out the 90mm macro this week and see how well it works, and think about what I'll look for when I go shopping again next month.