The druid is a very versatile class, so it's a good idea to consider what sort of character you're going for, and choose accordingly. Your choices of spells, skills and feats will vary a lot depending on whether you want to be a primary spellcaster, a sneak/scout-type, a mounted combatant, a shapechanger-type, a melee combatant, etc. And of course, you can do more than one of the above. Any preferences?
Some basic tips:
* The choice of animal companion will often affect the kind of role you play. A druid with a bear can be very helpful in melee combat but is going to have trouble traipsing into a tavern in the capital city. A flying animal companion like an eagle will be less effective in a fight, but less obtrusive.
* Druid spells are great at blasting and controlling the battlefield, and I personally find the latter far more useful. A carefully used entangle, soften earth & stone, plant growth, sleet storm, spike growth/stones, etc. can totally change the complexion of a battle.
* Depending on campaign style, Scribe Scroll can be a very nice feat for a druid, allowing you to be a lot more prepared for various eventualities.
* Two words - Natural Spell
* Take a look at Complete Divine. There are a lot of new druid spells in there. Just make sure that you and your DM are good at judging spell effects, because some of them need to be seriously nerfed (quill blast, for example).