From the camera, you might be able to increase saturation through in-camera processing. For post processing, you can always increase saturation through selective colour, Hue/Saturation or other options in Photoshop.
From here . Its a site with quite a number of PS actions, can try both the velvia and provia actions, i find both of these quite useful, esp if you dun want to mess around with selective colour manipulation urself.
What WB did you use? Maybe you could try WB setting -2 or -3 to give more warmth to the colors. I've also uploaded Dave's Midtone Boost custom curve, together with Auto WB -2 for most pictures and they turn out ok.
Colours function is found in menu, under the image adjustment thingy menu, u know the one where you select vivid, sharp etc.. just go under custom and change it there. BTW, I use sRGBI, and don't have any problems from recent shots
wah sad, you only have a little D70, no wonder colour not nice. (this isn't to be taken literally ...)
going by this thread, before the invention of photoshop, nobody could get nice colours.
1) that bouquet of flowers, looks somewhat underexposed by around almost 1 stop. have you tried to shoot that same thing with a different exposure? perhaps try bracketing ... go look for a subject with the same ugly colours and shoot it one stop brighter and one darker. see where you find the best results lie at.
2) i see some blue in the sky above. it was a blue sky day? or a muted, cloudy shadowless day? it looks a bit muted since there aren't any significant shadows around the bouquet. colours look more vibrant in more direct sunlight. without direct sun +/- shadows, dull colours might look more lively with a warming filter like an 81B for example. but again this is your age of photoshop so just click the famous "velvia filter".
3) ever tried some consumer pocket cameras? i hear they give nice colour. (again not to be taken literally.)