I have to look up these commands far too often!
Issuer
openssl x509 -noout -in cert.pem -issuer
Common Name
openssl x509 -noout -in cert.pem -subject
Validity Dates
openssl x509 -noout -in cert.pem -dates
Hash Value
openssl x509 -noout -in cert.pem -hash
SHA1 fingerprint
openssl x509 -noout -in cert.pem -fingerprint
MD5 fingerprint
openssl x509 -md5 -noout -in cert.pem -fingerprint
Full Details
openssl x509 -text -in cert.pem
Verify a certificate against a specific CA
openssl verify -CApath