Section 8 - also known as the container bar. http://www.section8.com.au/ When we first went there they didn't have a roof, just umbrellas on a string. Now they've gone all fancy and put up a roof/verandah
Next door - through the wooden door (no sign, never knew it's name till now) New Gold Mountainhttp://www.melbournepubs.com/venue/1937/ This place is cool and everyone thinks that you are great for knowing where it is.
If fake lawn, garden furniture and waiters in tennis outfits is your thing than Madame Brussels is for you http://www.madamebrussels.com/ Jugs of Pimms and Singapore slings, perfect for a late afternoon beverage. The food is overpriced and terrible, but cocktail jugs are great.
While on Degraves Lane go to the underground passageway to Flinders Street Station. I love the pink and black tiles, but there is also a gallery space, second hand shops and most often a good busker http://www.threethousand.com.au/keyword/degraves/
If gallery looking is your thing then start at the end of Flinders Lane and make your way back to Elizabeth Street, looking at all the galleries along the way. 45 Downstairs is great http://www.fortyfivedownstairs.com/ There is also a gallery on street level at 45.
Hosier Lane (between Flinders Lane & Flinder St) has the best city street art. It is where all the tourists go to view street art. The backstreets of Fitzroy also have good street art.
The Gorman and Mimco outlets are on Bridge Road, Richmond. I'd shop on Brunswick street if you have time. Also the Nova cinema on Lygon Street (walking distance from Brunswick St) has $6 movies on Mondays, if you're careful you can make at least three in one day.
With the short time you have I wouldn’t bother with DFO at Spencer Street. Generally a whole lot of shit. Time vs benefit comes out long on time and short on benefit.