Before I started using Pingoat I used to use Pingomatic and its still available but the list of services it pings its still the same and sometimes I get an error message on my first attempt and so not a very good alternative at the moment I guess.
I think the best alternative I have found so far is Pingates and this pings more than 30 services.
However, the only downside is that the captcha image is not very clear and sometimes it can be hard to see exactly what characters are in the image because the background and the letters can be nearly the same.
Another very good alternative I have used is BlogBlip and this pings more than 30 services and it gives you a summary of your feed plus the number of services pinged indicating succcess or failure. I found that to be very useful.
Also at BlogBlip you can download the current configuration file if you so wish.
Once or twice I have also used King Ping . King Ping gives a message saying that the pings have been send without specifying the particular services like what Pingoat, Pingates and BlogBlip does.
I am sure there must be many more blog pinging services but I think these alternatives are quite good and I also hope that Pingoat maintainance will end soon.