My favorite tool for checking DNS entries recently created a subscription model for their site. This is their right, of course, but I don't use their tool frequently enough to justify a subscription. Looking for a good replacement, I ran across intoDNS which runs an excellent free DNS check. I thought I'd link to them here in thanks.
I also like
What is a DNS check? If you own a domain name (such as mydnn.org) then you need to make sure that your visitors can find your web server from the name. Part of the Internet is to have Domain Name Servers (DNS) which make that connection for you. A DNS check will make sure that your settings are correct and will function properly.
Some other tools I took a look at: