Is there a console command, or any other way, to determine the level of an enemy you meet in game? Because I can't find it!

You can open the console (with the tilde key "~") click on the enemy and then enter the command "getlevel", then close the console by hitting the tilde key again

I think I've seen at least one mod that will show the enemies level without a console command. But I've never used it.

Well, everything is leveled in Oblivion, so you could tell by the enemies what level they are, IE Xivilai start appearing after level 22. Bosses are most times your level + 1. Here's a list for reference: http://www.uesp.net/wiki/Oblivion:Creatures

*facepalm* that's what I did wrong.. you have to click on the enemy after going into console mode, not just have him in the crosshairs.. thank you!