I got blank cards and envelopes from Tescos, think you get 50 in a pack and can choose white or cream.
I then went into word, put the measurements in and voila!!! a gift voucher.
on the front cover I have a generic design or something spa-ish
on the back cover I have all my treatments, my contact details and in the centre a mini version of the front cover
inside I have gift voucher printed inside if it Mothers Day I type that in too.
I have a stack of those so I can hand write who its for etc, but all my clients know if they give me a few days warning I'll print one off with their details in it:
eg
happy birthday mum
love you - enjoy a bit of pampering
Gift voucher for reflexology
love
Emma
I then print a mini pic on the envelope too.
I have also designed some on vistaprint and they are good.
I just bought a voucher from a local spa, they put it into a gift bag with a treatment menu and the voucher, but then put with it an ill-fitting envelope.
Love the idea of putting in samples, I have put tumblestones in the card before.