You Can Get From Here Good Sites For Ping http://updateseolink.blogspot.com/2013/07/free-top-high-pr-7-pr-0-ping-service.html
I don't think pinging is harmful it should be done under the controlled condition over pinging (I mean keep on pinging to the search engine is going to have adverse effect) but if proper .... then I is not that bad and like you said you are using WP cms, I don't think there is a need of pinging. In fact I am not pinging for my site rather than I was pinging it with personnel sites.
If you have quality website then you don't need to use any ping services as google will find your posts on its own... Why waste time on pinging then you can better use the time to come up with something interesting??? BTW, I don't use pinging services.
Pinging is useless, you really should read the case study - http://www.matthewwoodward.co.uk/experiments/index-backlinks-easily-revealing-case-study-results/ He clearly states that it's a sponsored post but he always independently tests the services and provides the raw data, in this case you can see what is the best pinging.
Thanks for sharing this list.....pinging is good when you see that your site or blog posts are not getting crawl by google. If you find that google is not crawling your site as before then you can go for ping just to remind the google about your site and blog....do it on timely basis....
As it has been mentioned time and time again even on this forum... There must be a reason why google doesn't index/crawl your posts. I used to have a site and when I posted then google was indexing my new posts within 2-3 minutes, then the site got penalised and it was taking days if not weeks for posts to be indexed. So I was using GWT to submit my posts, yes it worked and my posts were getting indexed right away but they were nowhere to be found in search results. So if one is so eager to get crawled quickly then why don't you just use GWT to do so????
yeah may be you are right but pinging is not harmful.Sometimes google crawl your blog but not inside posts so we ping it just to remind about your blog...and i am doing the same...and my blog is going good...