Drive Format

there's a write-up on wikipedia
also, you can google phrases such as "differences between file formats" or "difference between ext3 and ex4", etc

I agree with Marcus--these issues are widely written about on the Internet, and Wikipedia in particular is an excellent source for this sort of information. With that said, there are some specific considerations you may want to keep in mind:

(1) If you want Ubuntu to support permissions on the drive (so that different users on the Ubuntu system who have access to the drive have different abilities with respect to different files/folders on the drive, or so that you can mark program files on the drive as executable so that you can run them in your Ubuntu system), then you should use a Unix-style filesystem like ext4, ext3, or ext2. These are not the only Unix-style filesystems--for example, there's ufs, reiserfs, and a number of others.

(2) You should probably not use ext2 except for drives that will be mounted readonly or written to very rarely, or maybe for very small drives (i.e., up to a couple hundred megabytes). The journaling in ext3 and ext4 typically makes them superior to ext2.

(3) ext4 is a technical improvement on ext3, so you should typically only use ext3 instead of ext4 if you have some system that needs to access the drive that can use ext3 but not ext4. There are proprietary payware drivers for ext2 and ext3 on Windows, but I don't think there are any ext4 drivers for Windows yet. Mac OS X does not support ext2, ext3, or ext4.

(4) NTFS is readable and writable on Windows, readable and writable on Ubuntu (but NTFS permissions are not respected), and readable but not writable on Mac OS X. There are proprietary payware drivers for Mac OS X that let it write to NTFS. There are also, I think, free open source drivers, but they are very cumbersome and technical to set up. UFS, on the other hand, is neither readable nor writable on Windows, but is both readable and writable both on Ubuntu and Mac OS X.

(5) UFS is sometimes called FFS (it's useful to know what when researching).

With that in mind, you should be able to find the details, and other information, by researching, primarily with Wikipedia. But please feel free to reply if you have specific questions.

I need to correct something I said in my previous post.

I said that Ubuntu does not support/respect NTFS permissions. I was wrong.

By default, this is the case. And probably the vast majority of users accessing NTFS volumes from Ubuntu systems use this default configuration. But Ubuntu does have the ability to recognize and respect NTFS permissions, though there are some complexities involved and the parallels between Windows permissions and Ubuntu permissions are not exact. See http://b.andre.pagesperso-orange.fr/permissions.html.