Shopping around, I have come across a number of coin grading services... PCGS, NGC, ANACS to name a few. I have also noticed that I will see a coin graded PR70 graded by a company, then see the exact same coin with the same grade, but graded at a different company. But with some cases the prices are as much as doubled! Is this because some names go for more than others, or does it just happen to be a money hungry seller? Also, which names are the best and which do you want to most distance yourself from?

There are different types of grading companies. On the bottom end of the scale are companies what grade then sell their own coins. You can imagine they have a vested interest in saying the coin they are offering is a higher grade. What may grade as a almost uncirulated they may grade as uncirculated. Some tend to grade higher then others. (Same coin may grade as a 70 at some, 68 or 69 at others, etc. ) Right now the top grading companies are PCGS, NGC, ANACs, and ICG. With PCGS and NGC at top. Right now PCGS is commanding the highest prices followed by NGC. I.E. same coin in a NGC holder may go for less then the same coin in a PCGS holder even if the grade assigned by both are the same. Because the perception is NGC grades looser. Also changes in the persons grading at the companies or just changes in grading procedures will turn up differences in prices over time. A coin graded in the past as a 63 may stay the same or reholder as a 64 or 65 now. The old green PCGS holders normally go for a premium to another PCGS at the same grade because of the luck some people have had resubmitting them and getting higher grades. As to who to avoid check the second page of this link.

Oh jeez. Everyone prepare for some rants.

I have always considered PCGS and NGC to be about equal grading companies. I know some people have preferences one way or another (for example, I prefer NGC because I like their holder better)...but both are top tier grading companies. Now, with that said...it seems that PCGS coins carry a premium with it comes to coins graded a 70 (even over NGC). PCGS doesn't post their grade populations for free like NGC does (as far as I know) but I would imagine that PCGS grades far fewer coins 70 than NGC. I don't know for sure...but that would make sense to me anyway.

If you have coins worth more than $500 each send them to NGC or PCGS. Anything worth between $100 to $500 send to ANACS, they are cheaper and do a very good job.
I wouldn't bother certifying any coin worth less than $50, and I wouldn't use any company other than these three.

My two cents.

My fiance today went out and spent money and got a 1986, 1999, 2000, and 3X2004 silver Eagles. We were thinking about sending them out to get graded. Out of curiosity, we called ANACS, and they said that anything minted after 1964 would only be $10 to get graded (with a 5 coin minumum). This seemed like a pretty good deal. Are these coins with sending out? They really are beautiful...

That depends. If you are selling for bullon, then no. If you are thinking they are MS-68+ for collecters, then yes.

I am an advocate of slabs, but mainly as a way to guarantee authenticity and have at least some sort of grading benchmark (when learning how to grade and when buying over the internet).

But for coins like those silver eagles, there's really no need to get them graded by a third party. That is, unless you really think you have a perfect/near perfect specimen that would grade MS 69 or 70 by a reputable company. Most likely, spending $10 to grade each of them won't increase your pleasure of owning those coins. And when you go to resell them, having them in a slab won't net much more money than if you offered them raw.

Also, do not go with no name TPG's. I did and I was mad. Look under the thread IGS, I want my coin now. A good lesson in what not to do. I have since converted to ANACS.

Just about everything Mark Stilson said exactly. I go to about 2 to 4 coin shows a month and the highest prices for any coins are when they are in a slab graded by PCGS. NGC does OK, but mostly a coin has to be PCGS. I read somewhere there were as many as 107 TPG services. The greatest amount of them are fly by nights. I heard another rumor from someone that USUALLY, but not always knows what he is saying. He said the PCGS has or is buying NGC. Of course, like I said, usually but not always.
Regardless, as Mark said, PCGS will always bring a higher price.

PCGS is usually more highly regarded for US coins, but NGC is more highly regarded when it comes to world coins. IMHO.