Perhaps I teaching my grandmother how to suck eggs! But if you format the column ( say 'A' )you want to have the dates in then you can type in the first date ( in A1 ) - presumably a Sunday. Then in the cell below ( A2 ) you type "=A2+7", and that will give you the next Sunday. Then copy 'A2' as far down the spreadsheet as you want and all the dates will be Sundays.
About the next bit I am not so sure as I am looking for something similar myself. But I think if you want monthly or annual totals then get the totals added together, once you have done one successfully it's just a copy and paste exercise, and name the cell with the total in it something specific. Then it's just a matter of bringing the totals together, and you won't have to remember exactly which cells because the name will stay with the cell thats doing the totaling. And if you use cell names that reflect the day/date then you will be able to call them from anywhere. So if you were to call the first Sunday this year as "2011WK01", and the second Sunday as "2011WK02" you would be able to see the totals and for which week they represented. Of course if it's months you require that is slightly more complicated but it is still possible.
If I am incorrect I hope someone will correct me, but in the meantime the best of luck!!