This program allows you to index online headstones with easy. Also the users are the ones providing the images - I find this an easy thing to do. If you have a smart phone you can download the app (IOS or Android). Then you just get snapping. It's really cool. It makes the images and searches free to do as well so that's a plus. One bad thing about it is that it accepts one indexers view and that's it with no opinions. They do allow for edit later but that's little consolation.
Family Search Indexing
This is a longstanding program which is easy to do and allows you to focus on whichever project you'd like if there are images available for it. I would highly recommend this program to everyone as their indexes are made public and free for all to search. Also if you are doing a batch and having trouble you can easily share the batch for anybody else to view and assist you. The group on Facebook that I have begun to affiliate with is - Share Batch Indexing, ETC.
One of the great things about Family Search Indexing is that they always have 2 indexers so those records are looked at by at least 2 to form opinions and then a 3rd person decides which is correct. How awesome is that!!!
Family Search Linking
Just learned about this "beta" testing going on. Basically this deals with projects that have already been indexed but have lost their association with the accompanying microfilm image. Syncing these up is quick and painless. Obviously just as valid as indexing (Note: because this is beta the link I have may not be good for long)
Finally Ancesry's version
They call it World Archives Project and it does the same thing as Familysearch in a slightly different way. For one and most important to me: the final result is searchable only to paying subscribers to ancestry. I'm all about things being free or near free... ancestry's subscription model just rubs me the wrong way. Sad but true. I would contribute to this project once I learned there is an ongoing project that I would be able to be benefited from.
As I described earlier you can receive all records on ancestry for free:
"You can get access to ancestry.com's records for free by going to your nearest Family History Library find the closest one by clicking here "
Besides the above there are tons of online sites of indexed records and a few which allow you to input things you see. From my experience these are few and far between. Nevertheless these appear on google results and provide awesome information. Kudos to them!