My mother still asks me if I've remembered to say 'White Rabbits' on the first day of the month.
You have to say, 'White Rabbit, White Rabbit, bring me good luck' first thing in the morning before you say anything else, or it won't work. If you manage to do this, apparently you'll have a lucky month.
Had a look in the Penguine Guide to Superstitions, and it doesn't add much more that the info in Pete's link.
It does say, however, that it appears to be a comparatively recent custom - the earliest concrete dating is found in a correspondence from the Saturday Westminster Gazette of March/April 1919, where many of the correspondents regarded it as relatively new.
It adds that the basic principle involved is most probably the marking of a nother beginning within the cycle of months, but no plausible suggestion as to why it is rabbits has been suggested.
I wonder if there is a connection with the old Celtic hare? I found
this link:
"The hare was a sacred animal for Celts, a symbol of abundance, good fortune and prosperity. As a lunar animal, it represented the dawn, spiritual rebirth and the immortality of the soul. It was the totem animal of many moon goddesses, deities who were controllers of fate and weavers of destiny. The hare was an intermediary between mortals and deities, a celestial messenger, but also a trickster with powers of transformation and a bringer of change. Its erratic movements were thought to foretell future events. The word Easter is derived from Oestre, an Anglo-Saxon hare goddess of Spring, whose April festival celebrated the rebirth of the natural world."
The Celtic hare as a symbol of rebirth - saying White Rabbits at the beginning of a month? There may be a connection . . .
Carole
*edit* - the link above was for jewellery.
Here's a better one!