Hebe - lots of varieties. Euonymus fortunii - many varieties, evergreen and clippable. Neither usually gets to 3 feet though, not quickly anyway. Dwarf rhododendron? Skimmia can be kept low by pruning. Lavender if your soil isn't too heavy.
Pieris can be kept low by cutting back.

Fuchsia are also suitable and can be kept to size. Make sure you get hardy bush varieties though. Osmanthus is another nice shrub that is slow growing and can be kept to size.

Pittosporum come in a variety of varieties and all tend to be no more than 3ft.

Shrubby potentillas come in varieties with white, cream, yellow, orange, pink or red flowers.

Euonymus emerald n' gold and emerald gaiety, evergreen and brighten the dullest day, hardy too

Azaleas and dwarf rhododendrons, all sorts of flower colours, big impact, and the deciduous azaleas have good autumn colour too.

Most Skimmias only make about 3 feet - good in shade, as is Prunus Otto Luyken. In a sunnier spot, Spiraea Gold Mound (deciduous though), Euonymus Pierrolo - there are only two Pittosporums small enough - P. 'Tom Thumb' and P. tobira, but the latter is relatively tender. All the rest get about 9 feet or larger.