I don't know how many hours of sunlight you'll get during the summer, but cherry and/or grape tomatoes are good choices for container gardening - high yields and many have been bred specifically for container growing. Tomatoes like heat and sun, so if the balcony is short on that, they might not exactly thrive. Look for "determinate" types unless you want them rambling forever and needing support later on, though the advantage to indeterminate types is that they bear over a long period (vs. determinate, where the fruit ripens all at once over a brief period and then the plant is done).

For herbs, basil would be a good choice as a companion to the tomatoes. It enjoys the same conditions as tomatoes and it's the perfect herb to season tomatoes, too.

Another herb that I think is highly ornamental is borage, which has a tumbling, cascading habit, velvety silver leaves, and eye-catching pale blue flowers. The oil from borage is also HIGHLY beneficial for one's health, ranked even higher than garlic. The leaves and flowers can be steeped into a tea, or the leaves chopped and tossed into a green salad.

Hot peppers are good choices for containers as well - same conditions as tomatoes, though plant them so their "shoulders" touch. The foliage needs abundant sunlight, but the fruit can scald so planting them so they touch allows the foliage of the plants to shade the fruit.

For flowers: pansies, lobelia, petunias, celosia, trailing nasturtiums, verbena. Nasturtiums do best in lousy soil, unfertilized, with little care, so I tend to keep them apart from other plants which enjoy being fed and nurtured.

As for potting mixes - choose something rich in compost and organic matter for water retention and lightweight so that the containers don't weigh a ton when filled and watered. Look for a mix containing vermiculite or perlite. Many mixes are not "soil", per se, so bear in mind that you should fertilize regularly (except for the nasturtiums, which will provide abundant greens and few flowers if fertilized) and water prolifically. Containers dry out fast.

Another note on nasturtiums - both the leaves and flowers are edible and make nice additions to salad. The flowers have a somewhat peppery taste so are also nice pressed onto fish as it bakes or cooks on the grill. Pansy flowers are also edible!

careful with the borage.

http://forums2.gardenweb.com/forums/load/herbal/msg011656338203.html?3

Wow, interesting. Thanks for the link.