Raid 3 isn't used. I wouldn't recommend linear or raid-0 as they offer no redundancy. If your first drive goes bad, then you lost the entire array. The drive doesn't have to have a hardware failure. A bad block, a power spike, or going down uncleanly could mark the drive as bad.
If these are scsi drives, I would recommend raid-5.
For a web server, you may want to mirror the first 2 drives, and use the 3rd as a spare. Then one of the first two goes bad, the spare will replace the unit. You then have time to replace it.
Raid 0 (striping) will give you a larger array, and better performance. For better results on ide drives, don't use the slave connector. Ide controllers are cheap, so just add one if you need to.
If you had 4 drives you could use both striping and mirroring. The latest mdadm supports this. Some people have had problems setting up a raid 1+0 array and booting from it, and upgrading mdadm fixed it.