Wrt FS's, here was my Arch Linux setup (dualboot with Win 7 64-bit on an Alienware M11X):

sda 1 Win 7 boot
sda 2 Win 7

sda 5 ext4 boot
sda 6 ext4 /
sda7 reiser /var
sda8 xfs /home
sda9 swap

[I might've overlooked Arch's KISS principle on this one, but I thought I might as well go all out with a filesystem smorgasboard ]

And now? I've dumped Arch Linux for good 'ol Ubuntu. Got tired of constant issues after upgrades. Still probably the best online community and wiki for any conceivable subject; otoh, you end up there more often than I would like due to the "bleeding edge" nature of Arch. I'm happy to "settle" with Ubuntu for a while, until I need to bleed some more again.

Well happy day to me! NewEgg had a 500GB 7200.4 SATA drive on sale for $49.99. http://www.newegg.com/Product/Produc...m-_-22-148-374
Coupon code: EMCYTZT726

Now I'll have far more than enough space to add as many distros as I please. I can try them all in both 32 and 64 bit versions on their own partitions.

sda1 (ext4) Fedora 15 64-bit
sda2 (ext4) Fedora 15 32-bit
sda3 (ext4) Ubuntu 10.04.3 64-bit
sda4 (ext4) Ubuntu 10.04.3 32-bit
sda5 (ext4) Debian 6.0.2 64-bit
sda6 (ext4) Debian 6.0.2 32-bit
sda7 (ext4) Opensuse 11.4 64-bit
sda8 (ext4) Opensuse 11.4 32-bit
sda9 (ntfs or ext4) User Storage.

I just need to do a full read of the Debian, Ubuntu and Fedora install guides (wiki's) to see if there are any known issues with an NTFS partition on a boot drive and how I go about partitioning and formating a brand new, unused drive.

Your plan is very ambitious. Congratulations on finding a new hobby you like.

Personally, I'd definitively install only the 32 bit versions, only as virtual machines in i.e. Virtualbox, and use them to find the difference between the different distros. Only when I had fallen down on a single distro to look closer at, would I bother with partitioning, dual boot and 64-bit.

Because, you know... The task you describe is massive.

Volt - Thanks. It's better than reading/playing trumpet sheet music and microbiology research papers all day... I hope...
I'd agree that the task is a large one but it will provide me an opportunity to find installation problems with each distro. Learning each one will take a great deal of time and I'm best with just one, but installing them all and giving them a quick once over will provide me a reasonable view of each. I can always dump them by re-formating the partition the distro I want gone is on and combining it with what I listed as sda9 above.
I'm still liking the look of Fedora Plasma but Ubuntu looks like it will be the most functional and with the greatest support, so I'll start there (Ubuntu).

Okay, if it's just to install them, boot them up and take a few tours around the facilities, then you wouldn't really save a lot of time by using virtual machines anyway.

you can use ext4 for all distro.

Using a single 2Gb swap partition and then one ext4 partion for each distro will do with most of them (not for long term use, as you would prefer separate /home partitions probably). Most of the distro that won't accept that will work with one ext3 partition instead. For the rest, an ext2 /boot and an ext3/4 root should do, but I don't expect you to need that.

The most important part is to do a separate /home partition.. in that way you will always save your personal files.

For the system (rootfs) you only need between 10-15Gb.. the /home should take the rest. A typical disk will have.

10Gb /
4 Gb swap
rest /home

In your case you will have multiple system partitions. I would go with 64-bit which normally works great but sometimes need fiddeling. Like the flashplayer which just got an supported update. Before it had to be 32-bit... which can be run on a 64-bit system. For normal use 32-bit will be enough.. you will probably not notis any big difference.

I would go with what Volt said and try them out through VM first or as i said a usb-pen. Can be tedious to do that many systempartitions. Also go with Ext4 on all partitions.. no need to use Ext3. Btrfs are to early and Ext2 is too old.

But what ever you decide.. make sure to have just one /home and mount that to what system you are using.

Does it matter which partition "home" is? I was going to use sda9 in the arrangement I proposed. New hard-drive just arrived and I will be giving this a go tomorrow... I've quite the mound of reading to get through beforehand (at least Ubuntu offers a clear, easy to follow install guide which I can view on my life saving Nokia N900 as I work on the box ).
I'm swapping the Ubuntu and Fedora locations (Ubuntu sda1&2, Fedora sda3&4). Ubuntu was the choosiest of choices in this thread so I'll use it first (so long as it provides me fdisk, mkfs and fsck on install otherwise I'll have to Debian first which I know includes them).

No. some distro will auto detect on install if swap and /home partitions exist, for other you will have to set the correct number yoursef, but in the end you can do it for each. (actualy it is just a matter of mounting the sda9 partition in the /home folder at boot)

You will get prompted during the installation what partition you like as /home.. just chose manual while at the partitioner.

All distros will give you the same tools. If not they can be installed. They differ little in the backend on what commands you are supposed to use. I am not sure but fdisk, mkfs and fsck are all GNU. So those are sure to be on all.

When you are still at it.. i would recommend Linux Mint and Arch Linux too. Debian and Ubuntu are very similar in the backend (pretty identical) and you will use the same tools as on the N900 like Apt. With Ubuntu you should check out the PPA system. Fedora uses Yum and RPM. Arch uses Pacman and if you go that route i would recommend Yaourt for AUR (community unstable repo).