My non-religious tantra-yoga practices are (not quite complete, you don't have to give up your religion (or your atheism) in order to practise them):
* Use of water:
cold water after toilet used on private part.
I see someone already posted a more complete versions of these practices (accidentally moved by a mod to the Hindu DIR eventhough tantra-yoga is by no means unique to Hindu society):
Ananda Marga Yoga Society