I have most of the elite's unlocked and wanted to provide my opinion on some of the better ones.
Barrage. This skill is great for a bow with elemental damage. Pick up a fiery bow string and hit Citadel for IDS runs. The damage is great. If you want to augment it further you can be a R/E with the appropriate Conjure (name of element here)
Poison Arrow. This skill works great in a prep build. Remember Poison Arrow is an attack not a preparation as Apply Poison is. If you're fighting against any low health build (any thing 55) this skill is awesome.
Melandrus Arrows. This is a prep that may be useful in a degen build due to the length of the bleeding. Other than that I have very little use for this build.
Melandru's Resilience. This is possibly one of the most overlooked Ranger skills you will find. And thats for a reason. Energy regen and health regen are great, but I would rather have a monk get rid of all those nasty hexes and conditions wouldn't you?
Greater Conflagration. I like this skill, but I don't feel it can be easily applied to anything other than the R/Me Ettin farmer build found on this page.
Oath Shot. This is a wonderful skill in an Interrupt build or a group that has a tanker and wants you to run in and trap while they take the hits.
Finally we come to one of my personal favorite skills, Marksmans Wager. In all likelyhood this may be your first elite. I still use this especially when I do an interrupt build. I can interrupt constantly and never run out of energy. The one thing you have to remember is when you see an enemy throw up a stance or you have blind on you, time to put up the unguent and wait a few seconds.
I know I didn't mention several of the Elite skills including, Spike Trap and Practiced Stance. These are all just my opinions and would like to express them. Feel free to comment, but try to keep it positive and helpful.
Ranger Elite Skills.
Talon Berethin
Yolanda Kai
Only use I can think of for Practised Stance is for Choking Gas interrupter builds... decent prep if its duration was more than half its recharge under normal conditions 
Quick Shot is supposed to be nice for a spiker build, because it has a 1/2 second action time like Distracting. Never tried it tho, never bothered to cap most of the Ranger skills unless I'm totally convinced they'll work better than the ones I have for a specific build I wanna use.

Quick Shot is supposed to be nice for a spiker build, because it has a 1/2 second action time like Distracting. Never tried it tho, never bothered to cap most of the Ranger skills unless I'm totally convinced they'll work better than the ones I have for a specific build I wanna use.
ghostlyranger
melandru arrow do extra dmg to ppl under enchanment,
so it is actually quite good for pvp when use it with dual shot
so it is actually quite good for pvp when use it with dual shot
BBoy_Manchild
i dont go into CA without melandrus arrow in my skill slots, the number of wammos and monks and necros who use enchants outnumber people who dont
Yolanda Kai
That's true I guess, my W/Mo usually has 1-2 enchants on, sometimes 3-5 if healers are giving me some lovin. Any time there's a bunch of healers around you can bet Melandru's Arrows will be able to work at full efficiency.
Inureface
This may sound crazy but me and this spike group all used melandru's arrows as our elite prep for our spike. I saw 100s fly around and holy crap, it is GOOD. Dual and savage from 3 rangers under melandrus adds up to at around +70 damage, another 15 with order of pain, bleeding, and the +140 damage thing from dual shot (each shot will do +22). Love melandru's when I'm not going interupt.