I use strong crypto wherever I can, and naturally for email also. All email I send is either PGP signed or signed and encrypted with one of my keys.
If you receive email from any of my addresses without signature you should doubt its authenticity!
The only exceptions from my "all-is-signed" rule are mailrobots which can't cope with RFC3156-conformant emails and certain mailinglists. Exceptions for personal mail are only done on an as-needed basis for people with broken mailers.
My crypto tool of choice is GnuPG.
You can get my PGP keys (0xB963BD5F current, 0x42BD645D old DSA, 0x5B586291 ancient RSA, or 0xD81055B9 work)
or by dropping me an email with the Subject being
If you are using any kind of unixy system, you might be interested in my tool kuvert which automates signing and encryption of outbound mail.