I'm in the same boat. I have my father-in-law's camera collection to go through, catalog and evaluate.
I go in eBay and take the average value of what things sold at.
I also look at KEH, Adorama and B&H.
Camerapedia and orphancameras.com (butkus.org) is also a good resource.
There is a site called worthpoint.com that helps you find up-to-date prices/values on collectible items. It is a pay site, however. It might be worth it to you if you like the convenience factor or if you have a lot of stuff to evaluate but you can probably get the same information by going to other websites. Would you rather pay somebody to do the legwork for you? If so, Worthpoint is worth it, otherwise don't waste your money.
One thing. Look at your camera equipment with a jaundiced eye when it comes to putting a monetary value on it. Many people think they have a goldmine in old camera equipment but, unless it is rare and in really good condition it's not worth as much as you think.
Here's what I do. I take the TOP value I can find and consider that as the best price I can get if the camera was in mint condition. Then I rate the camera from 1 to 5 on several categories. (Lens/optics. Mechanics/film transport. Body/cosmetics. Accessories/case. Other.) I come up with a score for each category and take the average to get the camera's bottom-line condition.
Using the condition score, I mark down my top "mint" price to get the value I think the camera is worth.
So, let's say I have a camera I think is worth $150 in mint condition.
I score it thus: Lens=4. Mechanics=5. Body=3. Accessory=2. Other=4 -- Bottom line would be 18 out of 25. That's 72%. Thereore, my asking price for such a camera would be 72% of $150 or $108.
So, by my (admittedly arbitrary and non-authoritative) system, I would ask for $100 to $110 for such a camera, if I was going to sell it.
Also, don't forget, regardless of how much you think something is worth, it's only really worth what you can find somebody to pay for it. If you have an original Babe Ruth rookie baseball card you could say it's worth $1,000,000 and it might very well be worth a million. But, unless you can find somebody willing to part with a million bucks, that card ain't worth squat!
Negotiation is key! Somebody might offer you a half-million for that Babe Ruth card. You might be well-off to take the half million and be done with it. You might do well to ask for a bit more and see what the buyer is willing to give. Same thing with cameras.
My camera might very well be worth a 100 clams or even more but, unless I can find a buyer with a Benjamin burning a hole in his pocket, I've got nothing but a hunk of metal. You might be able to get $75 for the camera.
You can certainly sell things on eBay but, in reality, auctions are just another form of bargaining. If you post a camera on eBay and the price only bids up to $50 you are obliged to sell for that price, even if you think it's worth twice that.
I've got boxes full of Brownie cameras. Everything from Baby Brownies to Brownie Hawkeyes in varying conditions from near-mint to near-junk. Even the mint condition ones are worth, at most, $10 to $20 if I can find the right buyer.
It's all one big game, really.
For me, the bottom line is not really money. The thing that is most important to me is to find somebody who will appreciate (and hopefully use) the cameras that I offer for sale. That's probably the best I can hope for.
Money has to be secondary, really.