I have a blog on Blogger. I want to keep my blog private, but I have more than 100 invitations I want to send. Can you suggest what I could do? I don't want a public blog that anyone can access just by web search or people passing on my blogspot address.
You've hit a hard limit here. You can have a public blog or a private one. If you have a private one, you can send up to 100 invitations to people to read it.
Your only option would be for some readers to share the same password - but this would annoy them if they had to sign out of their own Google account and into the shared one to read. And if you don't trust people not to share your blog address, then you probably don't trust them not to share the account/password.