Also, I remembered right after I hit submit (of course):
You can walk along the canal all the way from just by Angel (Muriel St) to Camden and then along to Regent's Park which is amazing if the weather's not too bad!
Camden is well worth a look but it does get horrendously busy. You've got loads of ridiculous shops and then masses of stalls in and around the Stables Market.
On Mare St in Hackney there's a curiosity shop - Viktor Wynd - which is entertaining.
I'm sure I'll think of even more when I submit this but as you're only here for a weekend I'm sure you'll manage to find something to amuse you
*MySmiley*