From this page. formula 1:
=IF(COUNTIF($A$2:A2,A2)=1,A2,"")
Enter it in B2 and do a fill down.
From this page, formula 2:
=IF(ROW()-ROW(NoBlanksRange)+1>ROWS(BlanksRange)-COUNTBLANK(BlanksRange),"",INDIRECT(ADDRESS(SMALL((IF(BlanksRange<>"",ROW(BlanksRange),ROW()+ROWS(BlanksRange))),ROW()-ROW(NoBlanksRange)+1),COLUMN(BlanksRange),4)))
Enter it in C2 and do a fill down. Name the range B2:B8 "BlanksRange" and the range C2:C8 "NoBlanksRange". The two ranges must have the same number of rows (they don't have to be on the same rows, though).
Enter some values in the cells from A2 through A8. Try changing them. You'll see the lists in columns B and C change dynamically.
A sample sheet:
values formula 1 formula2
1 1 1
2 2 2
5 5 5
2 "" 7
1 "" ""
5 "" ""
7 7 ""
The two double quotes represent cells displaying blanks