you need to put them in an array or a recordset object and then sort that.
Something along the line of
Set objRS = Server.CreateObject("ADODB.Recordset")
objRS.CursorLocation = 3 ' adUseClient
objRS.Fields.Append "Name", 200, 50 ' adVarChar
objRS.Fields.Append "created", 7 ' adDate
objRS.Open
imagespath = "C:\inetpub\wwwroot\_images\"
Dim FSObj, FOlderObj, FileCollObj
Set FSObj = Server.CreateObject("Scripting.FileSystemObject")
Set FolderObj = FSObj.GetFolder(imagespath)
Set FolderCollObj = FolderObj.SubFolders
For Each item in FolderCollObj
Set SubFolderObj = FSObj.GetFolder(FolderObj & "/" & item.name)
objRS.AddNew
objRS("Name") = item.name
objRS("created") = SubFolderObj.DateCreated
Next
objRS.Sort = "created DESC"
objRS.MoveFirst
Do UNTIL objRS.EOF
response.write "<a href=""gallery.asp?gallery=" & objRS(0) & """>"
response.write objRS(0) & " <BR><BR></A>"
objRS.movenext
Loop