Quote from: pblack4 on April 06, 2014, 08:38:30 PM

What is the total number of nodes in the global bitcoin network?

Unknown, and impossible to know.

Quote from: pblack4 on April 06, 2014, 08:38:30 PM

so far I have found only this http://getaddr.bitnodes.io ..but I don't know if it's a reliable source

It specifically states:
"Bitnodes is currently being developed to estimate the size of the Bitcoin network by finding all the reachable nodes in the network"

After searching through their node list, I can confirm that my node is not listed there, so clearly it doesn't know the exact number. I have no way of knowing how accurate their "estimate" is.

Quote from: pblack4 on April 06, 2014, 08:38:30 PM

I thought there were more than 30K nodes earlier this year,

You might be right. How would we know?

Quote from: pblack4 on April 06, 2014, 08:38:30 PM

but the above website says 8K-9K

They might be right. How would we know?

Quote from: pblack4 on April 06, 2014, 08:38:30 PM

Is there any other website with historical info?

blockchain.info might have some historical info about nodes that they have connected to. I'm not sure if there are any other services providing historical info about nodes they've connected to.