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I see a lot of commercial online "solutions", but what homegrown stuff has helped you? Are we all just using Excel/Simple Access to do this?
used auto filter to sort against column headers like: paid, cancelled, attending, booked etc.
So it made it easy to filter out those who wanted to come who hadn't paid - or those who needed accommodation.
Used another worksheet with contact details and linked them.
I called it 'the oracle' - was quick and dirty - but really easy to update and everything was in the same place - of course I kept a copy online (protected) so I could access it from anywhere ;)
Don't know if that helps.