to encrypt a string using 3des algorithm:

echo 'somecleartext'|openssl enc -e -des3 -K 'some_key_in_hex' -iv 'some_iv_in_hex' |base64

to decrypt a 3des encrypted string:

echo 'somecipher'|base64 -d|openssl enc -d -des3 -K 'some_key_in_hex'  -iv  'some_iv_in_hex'

a bunch of symmetric encryption alorithms are supported, like AES, DES, blowfish etc:

Cipher Types
-aes-128-cbc -aes-128-cfb -aes-128-cfb1
-aes-128-cfb8 -aes-128-ecb -aes-128-ofb
-aes-192-cbc -aes-192-cfb -aes-192-cfb1
-aes-192-cfb8 -aes-192-ecb -aes-192-ofb
-aes-256-cbc -aes-256-cfb -aes-256-cfb1
-aes-256-cfb8 -aes-256-ecb -aes-256-ofb
-aes128 -aes192 -aes256
-bf -bf-cbc -bf-cfb
-bf-ecb -bf-ofb -blowfish
-camellia-128-cbc -camellia-128-cfb -camellia-128-cfb1
-camellia-128-cfb8 -camellia-128-ecb -camellia-128-ofb
-camellia-192-cbc -camellia-192-cfb -camellia-192-cfb1
-camellia-192-cfb8 -camellia-192-ecb -camellia-192-ofb
-camellia-256-cbc -camellia-256-cfb -camellia-256-cfb1
-camellia-256-cfb8 -camellia-256-ecb -camellia-256-ofb
-camellia128 -camellia192 -camellia256
-cast -cast-cbc -cast5-cbc
-cast5-cfb -cast5-ecb -cast5-ofb
-des -des-cbc -des-cfb
-des-cfb1 -des-cfb8 -des-ecb
-des-ede -des-ede-cbc -des-ede-cfb
-des-ede-ofb -des-ede3 -des-ede3-cbc
-des-ede3-cfb -des-ede3-cfb1 -des-ede3-cfb8
-des-ede3-ofb -des-ofb -des3
-desx -desx-cbc -idea
-idea-cbc -idea-cfb -idea-ecb
-idea-ofb -rc2 -rc2-40-cbc
-rc2-64-cbc -rc2-cbc -rc2-cfb
-rc2-ecb -rc2-ofb -rc4
-rc4-40 -rc5 -rc5-cbc
-rc5-cfb -rc5-ecb -rc5-ofb
-seed -seed-cbc -seed-cfb
-seed-ecb -seed-ofb