Just my 2p on these (with a slight PAL preference). Of the one's I've got...
39 Steps - Criterion R0 (1.33:1, NTSC)
The Lady Vanishes - Criterion R0 (1.33:1, NTSC, though a little low on the extras for the price)
Rebecca - Criterion R0 (1.33:1, NTSC)
Saboteur - Universal R2 or R4 if you like PAL (1.33:1)
Shadow of a Doubt - Universal R2 or R4 if you like PAL (1.33:1)
Notorious - Criterion R0 (1.33:1, NTSC)
Rope - Universal R2 or R4 if you like PAL (1.33:1)
The Trouble With Harry - Universal R2 or R4 if you like PAL (1.85:1 Anamrophic)
Vertigo - Columbia Tristar R2 (1.85:1 Anamorphic, whereas R1 is not Anamorphic)
North By Northwest - R4 if you like PAL and don't like snapper cases, R2 if snapper is your thing, R1 if you want the extra trailer. Personally, just for a trailer I'd only watch once compared to the film, I prefer PAL and sturdy cases, so R4 for me (plus it's cheaper and I can probably download the trailer anyway) (1.85:1 Anamorphic)
The Birds - Universal R1 CE (1.85:1 Anamorphic. R2/4 is non-anamorphic 4:3, though supposedly open matt)
Frenzy - Universal R2 or R4 if you like PAL (1.78:1 Anamorphic)
And a few others I've yet to get but have looked into...
The Man Who Knew Too Much (1934) - Carlton R2 for PAL and Amaray case, or R0 for the LaserLight snapper with a couple of small extras (haven't heard great things about the LaserLight editions though, although Carlton isn't much better).
Spellbound - R0 Criterion ?
Strangers on a Train - R4? if there is one. R1/2 are Warner snappers. R2 if you like PAL.
Rear Window - R2/4 for PAL (Rewind says R1 has DVD-ROM content, but I'd rather have a PAL version). (1.66:1 Anamorphic)
To Catch a Thief R1 due in November.
The Man Who Knew Too Much (1955) - Universal R2 or R4 if you like PAL (1.85:1 Anamorphic)
Pyscho - Wait for a better R2/4

. R1 may have extras, but it's the film I'm most interested in so if I bought it now I'd get the R2 for being anamorphic. Non-anamorphic NTSC of a 1.85:1 film is awful, even if it is black and white. Visible scan-lines, just can't stand them myself.
Marnie - Universal R1 CE (1.85:1 Anamorphic. R2/4 is non-anamorphic 4:3, though supposedly open matt). R1 has more extras.
Torn Curtain - Universal R1 (1.85:1 Anamorphic. R2/4 is non-anamorphic 4:3, though supposedly open matt).
Topaz - Universal R1 (1.85:1 Anamorphic. R2/4 is non-anamorphic 4:3 though supposedly open matt).
Family Plot - Universal R2 (R4?) for PAL (1.85:1 Anamorphic).
P.S. As well as Rewind, check out
MichaelDVD for some in-depth comparisons between R1s and R4s.