I don't know about you, but I always like to keep the listener stimulated, and there are various tools that one can use to acheive this, a natty bunch of melody hooks, or moving bass lines, brilliant lyrics, but Vocals are prime territory for adding interest, sometimes overt methods work well, but also sneaky less obvious ways also have impact.
Doubling a vocal is well documented here, but if possible always track a second and even a third vocal of the same line, the nuances of the difference in timings and delivery can be very useful, keeping it a few dB lower in the mix, panned slightly off centre L or R adds a "What's going on here" type of interest...
Rather than doubling manually, Antares make a plugin called Duo which does a pretty good job of add ing a seconds vocal, but it's boringly the same line at the same delivery, but it has it's place as does plugins like Eventides Quadravox, and Waves Harmoniser, but a live harmony line is so much more effective if there's not much going on in the background with the instrumentalists. It might be worth using automation to bypass the effect.
Tracking a line an octave lower can be great, and keep it very low in the mix, will again cause a few raised eyebrows, Soundtoys little alterboy can do this formant shift for you, but can sound a bit manky if it's too high in the mix (btw it can also make a female vocal sound like male one if you need to).
Shouted vocals from across a room and distorted (choose whichever way you want to distort, from bunging an inline fuzz box into a dynamic mike, to some posh saturation plugin like The Oven, or pushing your mic pre, or getting to close to the mic) can also be very effective...just watch the levels, I'd go with a plugin myself, as this can be reversed, an in line fuzz can't)
A slow flange on BV's, or my favourite BV thickener Soundtoys microshift works wonders...
Oh yes and chop any noise out of a vocal, home recording and a large diaphragm sensitive condensor mic will always pick up background noise...this is best done manually, but removing the noisey bits of waveform, it takes a bit of patience but it's worth while, gates are too insenstive, no matter which one you buy.
Danger it up....
Hope this helps...