I've got this site set up to require users to give a valid email address to request a new account. This being the case, I have the opportunity to see those email addresses.
The spammer who has been causing me annoyance today has emails that look like this:

bl.a.z.e.c.a.s.e.y.ol.omon @gmail.com
a.le.x.iva.n.o.vidr.ug @gmail.com
s.e.mautk.in.g.v.a.nfu @gmail.com

You get the idea. So when I see an email like that, I don't grant account access.

I've also banned access to people trying to set up accounts from specific domains. These include:

free-lesbian-pic.in
stanleykitchens-zp.in
bfkrnln.org
clothesbestsearch.info
avgustinotarapul.com
baggot.net