Beebo: if you don't like women shoes, have a look at KK outfitters. They've got great sport shoes. Also, check Beckenbauer's Doc Marteens.
Re. male/female clothes:
For pants: the major difference is that most women pants are generally low-waist. This is a design issue, not a mesh issue. If you make a pair of standard denims, going all the way up the waist, it will fit both men and women.
For tops: that's a different kettle of fish.
First, a mesh issue: the chest of the female and male avatar don't strech the same way (read: the male chest is a nightmare). This means you'll have to be careful with the placement of your design elements -- the nifty little logo, the bottle Wilhelm was talking about...
To see the difference, try shoving a vertical stripes texture on a shirt. Switch from a female to a male avatar. Now sit back and laugh (or cry... your choice!)

The second issue has to do with shading. That's not a mesh issue. It's an atanomical one. We girls have boobs.

It means that a woman shirt won't be shaded the same way, and won't have wrinkles at the same place, either. To see the difference, go to Tableau and grab the free tee-shirts. They have made a male and a female version, and the reason why should be obvious once you wear them.
Despite all of this, it is still possible to make unisex clothes.
For example, a sweater won't need strong shades like a tight cotton shirt does.
Loose clothes aren't too much of a problem, either.
Tee-shirts? I think you can get away with them being unisex. Be careful with the shading, that's all. Jackets should be fine, and trousers, too.
I advise you to make a few shapes -- standard male, standard female, busty booty female, testosterone-abusing male... and try your clothes on them. The results can be fun
