The first thing you have to ask yourself is what you're expecting RAID to accomplish for you. The next thing you have to ask yourself is whether whatever gains RAID gets you toward that goal are worth the extra hassles and risks that RAID brings to the table.
If you want to PROTECT your data, you could use two disks in a RAID 1 (mirror) configuration. This would protect your data against a drive failure - but you'd still need to back your data up to safeguard against the many other risks to your data that RAID can't protect you from. RAID 1 gives you half of the available storage space of the drives you use (ie, two 1TB drives in a RAID 1 volume gives you 1TB of usable space).
If you want to improve PERFORMANCE, you can use two disks in a RAID 0 volume to improve transfer rates. But RAID 0 doesn't improve access times, and if EITHER drive fails then you loose ALL your data (and two drives are twice as likely to fail as one drive is). You don't loose any usable space with RAID 0 (ie, two 1TB drives in a RAID 0 volume gives you 2TB of usable space).