In terms of tracking how successful your anti-spam measures are, you will not have a great deal of luck with this unfortunately as a lot of spam filtering software simply drops mail that it believes to be bad. However, well-behaved anti-spam systems will reject (at SMTP time) the mail: so, you could capture the rejections if you have a valid return-path for your outgoing mail. Make sure the Sender: header is set to an address of yours which will receive mail so that the bounces end up there.
Some of the big ISPs support providing sites with copies of mail they have identified as spam ("feedback loops"). E.g. AOL does, see http://postmaster.aol.com/fbl/fblinfo.html . This would mean you would receive a sanitized copy of mail that they had received from you and had been marked as spam.
You will find some users are very lazy and rather than follow even very clear or easy unsubscribe instructions, will just click "spam". Even if they opted in explicitly in the first place. Feedback loops can help you identify those users although it's not trivial because the loops are sanitized precicely to stop you identifying the users!
Finally keep an eye on popular RBL lists to ensure your mail servers are not listed. Some of the popular ones are listed at the wikipedia page "Comparison_of_DNS_blacklists" (no direct link, sorry, only one URL per answer for me!)