There are probably many other captcha solver services out there but I am going to compare only two because these two I believe are the best. I thought that Death by Captcha and Captcha Trader have developed OCR technology to solve captchas like those of Google reCaptcha.
Turns out they employ a system where they have users working on hand to solve the captchas sent to them either through the website or through any of their programming language APIs.
Both have advantages and disadvantages that put themselves on top of the other in terms of feature and I will go over them 1 by 1. These factors can help you decide which service you may want to prioritize using. In my case, I use both of them wherein one will service as backup in case the first one does not produce the right answer.
I have to give this one to Death By Captcha. The first time I tried it, it gave me the correct answer and I was impressed because I thought their OCR technology really worked (later on finding out that users were the one behind the correct answers).
Captcha Trader gave me a wrong answer when I tried their service and the answer was way off. Although this does not mean that they have low accuracy for correct answers, I based my choice on the first impression.
I will have to give this factor to Captcha Trader. While both lets programmers supply image URLs of the captcha, the problem is when they give out an incorrect answer.
Captcha Trader records image URLs of captcha so you can ask the system to refund the credits used back to your account.
Death By Captcha does not have this feature. The system requires you to upload a physical image file of the captcha in order to do a refund so if you use image URLs, then there is no way to have it refunded back to your account.
Captcha Trader gives free credits when you make an account. These are especially useful if you want to check if it works with how you want your program to use it. You can buy more credits or you can earn them for free by answering other captcha submitted by other users.
Death By Captcha does not have free credits to start with although I did email them to ask for some so I could first test their version. They have no way to earn free credits though so if you want more credits, you have to buy from them.
Both have Java (as well as other programming languages) support so this is a tie for them.
Both do respond in quick fashion but I will give the win for this factor to Captcha Trader.
Because of first impression, I use Death By Captcha first and use Captcha Trader as backup in case I get an incorrect answer on the first try. However, once my Death By Captcha credits run out, I may try to see if Captcha Trader can work itself efficiently.
Free is tops. But maybe accuracy is more important to you. The choice is yours.
EDIT: After using it for many months, CaptchaTrader does it more efficiently and you do not have to pay for it so long as you answer some captcha yourself to be able to earn credits. The sad thing though is that now, CaptchaTrader is dead.