I'm running out of disc space and looking to get new drives.

1 - My current boot is a 150G velociraptor. Would this be better served as a rendering/transcoding disc?
2 - Would it be even better if I had a source and destination velociraptor?
3 - Is there any reason to have 10k rpm boot disc over a 7.5k boot?
4 - What is the consensus for setting up a RAID? WD has a SATA III 1TB drive out for a reasonable price. I'm thinking of getting 2 for some sort of RAID, but have never delved into this before.
5 - Now that I've made a few "movies" I'm finding what to keep and where to keep it to be a lesson in chaos. What do you do?

I make movies to see what's inside my head. No other delivery intentions

Thanks,
Burt

1-4: Opinions will certainly vary on this.

One approach would be to add an internal or external drive for projects.

The next step, if render times were not what you wanted, would be to figure if they were processor-bound or disk i/o bound. If disk, the next step would be to add another internal or external drive, which might be a renders drive, the other becomes the source/projects drive.

If your projects involve multiple HD streams a RAID for source can help previews.

Current price/performance suggests SATA, eSATA, and NTFS-formatting for everything.

Were it me, I'd keep your 150GB as the system drive and add a drive and see where it gets you. If you get satisfaction out of having the fastest system around, then by all means do all of it!

5: Project organization is a challenge, yeah. There are probably as many methods out there as there are editors. The directory hierchy of my project drive is as follows:
Drive
Folder-Projects
Folder-Project name and month-year
All vegs with version numbers, All project documents, Folder-Raw (source), Folder-Renders, Folder-Graphics

I also have external Archiving and Project Backup. Previously, that was raw PATA drives I installed in external USB/FW cases. Then, I started putting everything in a removable cartridge system.

Currently, I'm using a hard-drive bay gadget that allows you to shove in a raw SATA drive.