I have had this request umpteen number of times. Whenever someone wants to organise Bingo/Tambola/Housie at their parties, they end up writing the cards themselves, as most of the Bingo kits come with very few non-reusable playing cards. Most of the sites which turn up on searching for Bingo cards produce cards which are not the regular 6 cards in a sheet 1-99 kind of cards. I have never gone so far into google searches to find this site.
So, here it is, the site for automatic bingo card generation. This site generates one sheet at a time (12 cards, 2 columns). Just keep pressing next and then fire a printout. Cut out the columns/cards and then distribute. Enjoy!
Update: There is another Tambola ticket generator which is much better than the above with lot of customization options. Check out http://tambolatickets.kunals.com/