Measurements are the bane of my existence

Graphic novels? Generally, no. Some specialized publishers have standard trim sizes (Tokyopop, etc), but most others seem to publish a range of sizes and shapes. So it really depends on which publishers you're considering.
The book my agent has out on submission is ~5 x 7 1/2, and the one I'm working on right now is 6 1/2 x 8. I came up with those numbers myself, looking at what's on my shelves and how I want the books to look.

Also keep in mind that you generally submit only a finished chapter or short sample, not the entire drawn book. If the publisher does have a specific size they want, you can adjust (or redraw) that portion, and produce the rest at the correct size.

One hint: draw larger than you want the pages to be, though Some people blow up their guidelines and print them out onto 11x17" pieces of paper-- when they scan them back in, they shrink them down. You don't have to go that large, but drawing bigger than print size is strongly recommended.

Also, be sure you understand what "trim" and "bleed" are!

This should help you immensely: http://store.comixpress.com/faq/technical.php

Trim: 6.625x10.25”
Live Area: 6x9”
Margins: Top: .5”, Bottom: .75”, Sides: .3125”
Bleed: 6.875x10.5”

ETA: Comic book pages are drawn on 11 x 17 boards and reduced (thought computer drawing is changing that). That may be a helpful start for you.

Welcome! We look forward to seeing more of you!

Just to confuse the issue, if you intend to provide computer rendered art you should use at least 500 pixels per inch for b&w or 1000 pixels per inch for color, so that the resolution isn't compromised in printing.

IIRC, most non-digital comic artists work on 11x17 Bristol with 1/2" margins right, left, bottom and 1" margins top. When I get home, I'll drag out some of the comic art I've bought and see how close my memory is.

If you want to get these publishable, you're going to have to deal with pixels and DPI at some point, heh. Just how it works. Most publishers I've worked with have me upload the files to an FTP or send a CD-- no one wants the paper and ink pages. You have to scan and prep them yourself.

I've had publishers ask for 300 DPI, 600, and 1200, and a few others in between. It all depends on if it's black and white, grayscale or color.

I recommend checking out this blog:
http://comictool.blogspot.com/2009/08/sorry-about-corroded-silvering-in-hall.html
That entry in particular goes through part of the drawing/scanning process step-by-step, and there are plenty of other posts like it. Ignore the posts about knives and things, but there are lots of helpful tutorials (word balloons, etc).