This might be somewhat of a religious issue, but here goes.
I have a new hard drive and I am setting it up for dual boot (Windows/Linux)
I am going install Debian Etch.
I am using GParted to format the drive.
Which filesystem format do I choose for the linux side?
ext2, ext3, reiser4, reiserfs, other?

ext3 is sort of the standard--do you have a reason to use something else? (If you don't know, then you probably don't)
With ext3, you can get Windows tools that let you read your Linux partitions. I use Ext2Fsd, which works great.

You can also set up a shared FAT32 partition for shared data, but you cannot set permisions on FAT32.

Finally, be sure a leave unpartioned space for later changes. It's easy top add partitions, and re-sizing is a pain.

ext3 it is then.

>>be sure a leave unpartioned space for later changes. It's easy top add partitions,
What would I change later?

Ext3 is the most native filesystem on Linux. Most comparisons recommend either ext3 or reiserfs for desktops. They offer support for things like acl's, journaling and quota's, and are robust if you have a crash, or accidently power down. For high-end database, webservers or media servers, that are up all of the time, other filesystems tend to be recommended. ( JFS, XFS, etc )

You may want to use google with the terms "ext3 reiserfs xfs jfs" for sites that have done head to head comparisions.

Just some anecdotal info but I had reiserfs partition get bad clusters (well it was an old HD) I kept trying to gather up all may data and fsck.reiserfs just seemed to make it worse. Then I heard about the Mr Reiser's difficulties, and decided my new HD would have ext3. That said, reiserfs seemed a bit faster. But ext3 is less angst filled.

I would recommend having the /home directory in it's own partition. Then you can reinstall or install another distro while keeping your old /home partition, but reformatting the others. Even if you rename your home directory, such as from "allepath" to "allepath-bu" and create a new "allepath" user, you can post install, move your personal files to the new directory, and delete it when done.

Some distro's use different ranges for UID as well, you might need to use "chown -R allepath:allepath /home/allelpath-bu" to be able to access an old home directory. The convenience is worth it.

For workstations, where you install the latest and greatest programs, the /usr hierarchy tends to grow in size over time. If you create a separate partition for it, the suggested size tends to be for servers and is too small. Use twice or three times the recommended size.

If you keep the /usr hierarchy in the (/) root partition, you have the option of later adding another disk drive, and moving the contents onto it's own partition on the new drive.

If you will be doing things such as creating DVDs, then you may want 5 GB available for /tmp. On a workstation, /tmp is usually a directory under the root partition. On a server, /tmp is usually separate so that you can mount it with the "noexec,nosuid,noguid" options.

SuSE is moving from reiserfs to ext3. They claim they made the decision because the current reiserfs version they use wasn't being actively developed and the reiserfs v4 wasn't ready for prime-time. But the arrest of Dr. Reiser may have had something to do with it as well.

Ext3 isn't the most efficient because it is designed to be the most compatible on all linux systems regardless of the architecture. It is a good choice because of full support in linux for extended attributes, ACLs and quotas. If you find a howto on using quotas or ACLs, they will just work because you are using a filesystem that supports it.

If you have a reiserfs /home partition, the default boot kernel of another distro may not recognize it without modprobing "reiserfs" after the boot and before partitioning. Also, if you need to use a lightweight live distro for rescue type work in the future, using ext3 will guarantee that the filesystem will be recognised.

If you are building something like a video server for your home network, you probably want to do some comparative study before deciding.

I put a fairly heavy value on the filesystem that my preferred distros (Slack, SuSE) use as the default. Last time I checked, it was reiserfs for both. I've experienced zero problems thus far.

That said, ext3 is equally strong.

I've got reiserfs on my laptop and desktop. ( Except for the boot partition. )
My main reason for suggesting ext3 is because the original poster may plan to try different distro's. If the boot kernel doesn't load the reiserfs module, or if it uses lilo, and the reiserfs partition wasn't mounted using the "notail" option, a newbie may have difficulties.