i would say, vaccum bags are already a passe creative invention for minimising the space in a pack.
i have stopped using ziplock bags now that i found another way to pack my clothes. they call it the Pack-it-Sac.
it is a a4 size zipped bag, with 1 - 1.5 inches allowances along the perimeter of the bag. the bag opens along 3 sides of the bag you can easily pack in 10 tops inside (folded nicely) and then zip the whole thing up, and put it in your pack. its way better than ziplock bags and ziplock relys on your butt to get all the air out in the bag but the pack-it-sac is able to compress your 10 tops liek the ziplock bags easily.
so far, i found such bags only under the brand, eagle creek.
so try checking it out.
I used a combination of vacum bags for my winter clothing and the pack-it-sac for my other clothes. Its great to keep your bag organised.
Huishan: you might want to go to sports connection (since you are in Singapore). They have their own house brand (bodypac) and teh pack-it-sac is alot cheaper. S$9.90 for 3 bags of different sizes. A cheaper alternative to eagle creek.