The shorter dress set with a hemline on or above the knee should be your wardrobe staple for spring - the chic dress is very fashionable for 2007. 
For the brave and fashion forward with good legs, the ultra-micro mini or tunic dress is the main purchase.  If your arms have lost their firmness you will find plenty of elbow sleeve and longer sleeved dresses in the shops.

When you are older then a dress grazing the knee is always the alternative to the shortest looks.

When dresses on offer are too short for your taste or nerve, then it's still acceptable to team them with skinny trousers, leggings or coloured tights. If existing dresses have the balance to be shortened, then shorten your dresses.  Start pinning them up now to check how they look.   If your legs look wobbly get going on some daily walking or lunges!