To be honest, it's the tail end of the rhubarb season, so it's going to be a little tougher than early or forced rhubarb, so I would avoid making anything that doesn't require mullering.
Make jams, compotes and purees - they can either be kept in the cupboard forever (the jams) or frozen (the purees).
If you want to make a crumble for freezing, there's no sense in freezing the whole thing - just the fruit. The crumble part, after all, takes about 10 minutes to prepare, and is not exactly seasonally available.
Be careful not to leave any stalk up your jacksie for too long though - The oxalic acid in the stems leaches out over time, and will cause your derriere to loosen to wizard's sleeve proportions, whilst your entire lower half would take on a luminescant turquoise hue.