The more I read, the more confused I seem to get when it comes to a good partitioning system. And any articulo that gives examples is doing it with a one drive system, and fairly small by todays standards; I have no (permidently installed) hard drive smaller than 100gb, and there are 3 hard drives (2 are bigger, that is just the smallest one!).
So here is the deal.

1 - 100gb
2 - 200gb
For a total of 300gb of hard drive space.
1gb ddr ram
2.8ghz CPU

I'm going to want a small partition for FreeDOS (Maybe 10 or 20 gb, that may even be too much). The rest (once I backup all data on them) for Linux.
There is probably (not including root) going to be 3 user accounts. Possibly 3-4gb worth of .MP3 files (playable by all users), no video files permidently on the system, but lots of video DVD ripping, burning, authoring as well as video capture/edit. Not too much software developement, but a little maybe?
Some Spreadsheets, word processing, exc. On OCCASION serve a few files (all types) via FTP - but no "permident" server, just basically to make it convenient for friends and family that live pretty far away to get files from me.
So, any suggestions on a decent partition setup for that?

Personally, I would do something like this:
1gb - Swap (Equal to your RAM, maybe double it to 2gb since you have so much space)
256mb - /boot
2gb - /var
2gb - /tmp
36gb - /
Remainder - /home

That's my personal preference, and a lot of it is based off primarily running servers, so maybe not appropriate for a home machine...

EDIT: I'm also suggesting that you'd use LVM to combine the 2 drives into one

If looking for some sort of failover setup RAID 1 as well. LVM is also a very good idea as its good for future expansions.

This confused me also when I first started out with Linux. fukawi2 has good suggestions mentioned above, I'll build on what he already suggested.

I would bump /tmp up to 4gb since your doing mp3 and video. Some of the video ripping pgms use lots of /tmp space.
I would make / a lot smaller, maybe 10gb
and add a /usr with 30gb. I like to separate / and /usr
If you plan to share the /mp3 files amongst all 3 users you might also create a /mp3 file system and make it 100 gb or so. But you can add that after you build your system.
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For other newbies building a test system I found it very convenient to build a system with only / Everything is then put under root, and you don't have to worry about sizing things right. The downside is for you can't backup or restore just /home or /usr since everything is seen as one huge filesystem. But when starting out and not knowing what size to make things this is a good way to start IMHO.

Are you sure you want to spend all your free space on a single Linux distribution? I have a bit of space on my system (1000GB) and I installed no less than a dozen OSes. Sure, it's nuts, but now I can compare at my leisure without kicking off one OS before I'm able to install a different one. With 300GB, you could easily install a few yourself.

I'm not too concerned about that. If I do want to try a different distribution I'll just install it to that "Internal" hard drive that is NOT actually mounted in my case (like the OS install I am using right now). That is one of the purposes of that HD (it's not mounted in at all, so that drive is effectively "portable" even though it's a "Internal" drive, it just means unplugging one IDE cable, and plugging in a different one, and grabbing power from somewhere (easy enough). This is why I call that my "Test HD" - it's only used for testing thing, and sometimes quick data dumps so a HD can be re-formatted, without spending a lot of time burning CD/DVDs (copy to the "Test HD", format, (if an OS was on it, re-install it), and copy all data right back (this works regardless of the OS, just format the "Test HD" with a file system the OS you are working with can use. (NOT NTFS if the base OS is Win95/98/ME !!!)

I agree with this. If you are not sure how to organize it, do it this way. By the time you figure out how you need to allocate the disk space, you will have also figured out how to fix it with minimal effort.

Well

I've been doing multi-boot for some time now, I use bootitng boot manager for a few good reasons, it's a one tool does all including: make partitions, re-size partitions, slide partitions, boot multiple OS's, wipe partitions/drives, and the best part, makes compressed images of a partition or volume. Here is my current scheme in order on a 250GB sata drive:

Bootit EMBR.....7MB
Windows Media Center.....15GB
Windows XP Pro (playground).....15GB
Linux Fedora Core 6 64bit.....10GB
Free space for future Fedora or Mandriva expansion if needed.....5GB
Linux Mandriva 2007 64bit.....10GB
Linux swap.....2GB
Linux Debian Etch 64bit.....10GB
Linux Mandrake 10.2 32bit.....10GB
Linux Fedora Core 6 64bit (playground).....10GB
Free Space
NTFS data partition.....110GB

I have no separate /home partitions as all Linux OS's have ntfs-3g installed, all from source except for Debian where I used ntfs-3g.deb from repo. The "playgrounds" are for testing software and the likes that I'm not ready to implement into good copies of the OS's. All partitions are primary partitions and all OS's can be restored from an image off the data partition in less than 10 minutes including wiping the partition with zeros first. All OS's can access the data partition. Any OS image can be added anywhere on the drive as many times as required like the two FC6 that are derived from the same image because of the boot manager's features, (FC6 has been a bitch with "dependency hell" so I work out the dependencies in the playground first). If I need extra space for authoring DVD's , I set the application to use the data partition for temporary space. When my 30 day trial authoring suite's 30 days are up, I spend a few minutes wiping out the playground (Windows) and re-load an image...re-install another 30 day's trial. It don't bother me to get a virus in Windows as it only takes a few minutes to get a fast, fresh, fully updated installation back in it's place. All applications and updates are also stored in the data partition avoiding using CD's or downloading updates off the internet when needed.
This is my system, the OS's are always in tip top shape and run fast, I only install software/packages when needed off the data drive, not load up the system from the get-go and bog it down. Having smaller / partitions also improves performance. The biggest partition should be similar to mine, a "shared data" partition with everything on it. My computer is in another room, I can't be bothered running there to put discs in the drive. Everything in my data partition is backed up on a 120GB external Fat32 drive including the images of all my OS's . The external drive is Fat32 in order to be backwards compatible for customer's computers for my repair business.
Windows Media is a heavy OS, it's compressed image is 2GB in size, the Linux's are around1.4GB in size.