Do you want foliage or blooms? Impatiens, begonias and such provide summer blooms. Hostas, heucheras and ferns are excellent foliage plants.

There is ONE impatiens Fusion 'Peach Frost' in my container from last year! I also had coleus, begonias and the draceana in the pot: {{gwi:561499}}From more info on my container

Here is a link that might be useful: my links to container garden recipes

Thanks for your reply. In my original message, I said more about what I was thinking but I was having problems posting. I tried begonias last year and they did ok but I am actually making tipsy pots so the pots do not sit flat.
A tipsy pot is made by stacking pots on a rebar pole. The pots rest on each other and are stacked but tipsy so that
you can plant something in them. Petunias would work really
well but they need sun.

The variegated Hakone Grass, Hakonechloa macra 'Aureola', would look beautiful in that type of potted situation. The way it grows makes it look like flowing water, only yellow and green instead of blue. Many of the Sedums will take some shade. Browallia is an annual that comes in purple or white and has a drooping, spreading habit, so it would look great, too.

Lamium (dead nettle) is a perennial that might work well. I love browallia but can never find it!

I would try Torenia and the little Impatiens - both will need to be trimmed back after while, 7 inches ain't much room and these guys are aggressive spreaders. You could also try one of the creeping coleus, they have smaller leaves and kinda drape over the pots edge... they came out a few years back and I haven't seen them around much lately, but I haven't been looking for them either.

Thanks everyone for these wonderful suggestions. I will write them down so that when I go flower shopping I can keep an eye out for them. It took me forever to get back on to see if anyone had replied. Been busy. Great that it is finally spring!

boy...I vote for torenia. I tried it in a dry odd spot..full hard sun until lunchtime then hard dark shade thereafter. It absolutely thrived and was still blooming when I pulled it out in November.
Bet it would be perfect in a pot in shade.