Great sites for finding & checking email headers and IPs

This is one I use all the time.
http://whatismyipaddress.com/

You can check where an IP address leads to, see if it's on any blacklists and also copy in email headers to find their source. It also shows you how to find the headers on several email clients.

I use myself this one http://www.iptrackeronline.com/header.php its also good

^^Both good. And here is another one: http://www.ip-adress.com/trace_email/?sr=1

Use this to check if IP is abused

http://www.stopforumspam.com/

We provide a "free for use" site where you can check registrations and posts against our database We list known forum and blog spammers, including IP and email addresses, usernames, how busy they are

very useful

http://whatismyipaddress.com/find-headers has a list of the most popular email providers and how to find the headers with them.

Another useful site to find emails headers:
http://www.spamcop.net/fom-serve/cache/19.html

Just copy email header and past into one of these tools (IMHO, the top 2 are the best):
http://www.iptrackeronline.com/email-he ... alysis.php
[XXXXXX] http://www.ip2location.com/free/email-tracer [/size]
[XXXXXX] https://toolbox.googleapps.com/apps/messageheader/
http://tools.appriver.com/AnalyzeHeader.aspx
http://mxtoolbox.com/EmailHeaders.aspx [/size]