You can select a combination of early, mid-season and late bloomers. Visit any decent garden center or your favorite gardening website to see the hundreds of choices.

Dwarf irises, species tulips, crocus and narcissus, grape hyacinths, chinadoxa and scilia. Note all the bulbs I have suggested are quite short, being ones used in alpine beds. You could also think fritillary and taller irises.

Well there are other choices, but just because they're bulbs, doesn't mean they all like the same growing conditions- some do better in shadier spots, so you need to check out the growing requirements for each before selecting if you've only got the one pot. Eranthis, Galanthus, Leucojum and Iris reticulata are the earliest, then there's Anemone blanda, Puschkinia, Scilla tubergenia, Erythronium, Chionodoxa, Convallaria, the Fritillarias (F. meleagris and F. iimperialis), Muscari, Hyacinth, Trillium, Ornithogalum, Tritonia (May-June). Many of these are low growing - I haven't mentioned crocus, narcissus, tulip because you said you wanted something different. There are others flowering May and June, (Sparaxis for instance) but they generally need lifting in autumn, storing somewhere frost free and then replanting.

There are literally hundreds of choices plus there will be new ones just hitting the market for the first time in the Fall.

Dwarf Bearded Iris (MB & MTB), Ledebouria cooperi, Narcissus poeticus hybrids, and Scilla [Oncostema] peruviana.

Thanks everyone definitely given us some good ideas.

If you only have one container and want a succession of blooms why not plant in slightly smaller pots and sink them in the container compost in turn as they are ready to come into flower. Its easy this way to plant them out into the garden afterwards, and if you grow some iris reticulata they can be left in the pot somewhere dry when the leaves have died down and they will come again if replanted next year.(This is the only way I can keep them from year to year)