well... :/ I Don't think there is a way to just have a list populate that displays the size of each worksheet. There may be a VBA code for this that one of the ninja's could provide.
Give a look at this post: http://chandoo.org/forums/topic/need-help-with-a-macro-to-make-file-copy-without-macro#post-24026
It creates a workbook with all worksheets without macros. You can modify it yourself to create individual workbooks for each worksheet. That would give an approximated size, because a workbook isn't exactly a worksheet, but's better than nothing.