Welcome to ENWorld!
1. Evard's Tentacles isn't a Druid spell. Maybe you were thinking of entangle?
2. In my experience, an animal companion with pounce and many natural attacks is the best for sheer combat power. Basically the wild cats line. Leopard, Lion, Tiger, Dire Lion, maybe Smilodon (sabre-toothed tiger, from Frostburn). Don't do Dire Tiger, though. I had a "cat lady" druid and discovered the benefits are kinda better if you just advance a regular tiger, unless you want to go for sheer HD. Which is useful, for things like Blasphemy spells and getting more feats... Back to the original point, Dire Wolf only gets one attack (two eventually, thanks to companion boosts) and a trip check on it. I'd rather have a pouncing Tiger making 5 attacks. Complete Mage has a variant rule to get a companion elemental instead, if you like.
3. Can you be more specific in what you'd like to do? Druid more than most other classes really has incredible room for growth in many directions.
If you want to focus on summoning, my friend made a pretty nasty Wizard/Druid/Arcane Heirophant (dual casting class, Races of the Wild). He used the Unearthed Arcana Conjuror variants to great effect, also found here:
Specialist Wizard Variants :: d20srd.org
[sblock]Rapid Summoning is just plain worth it (note it only affects Summon Monster Spells, not Summon Nature's Ally). Enhanced Summoning is also worth it, giving you Augmented Summoning w/o the largely worthless Spell Focus feat. And if you want Scribe Scroll, you can just pay a normal feat for it, so you end up getting Augmented Summoning and Scribe Scroll w/ 2 feats instead of 3. The last variant might be worth it, up to you. This build will have lots of spells to play with, so it doesn't hurt too much.
Now you have Druid side for spontaneous summoning, and Wizard side for quick (standard action) summoning. Also check out Frostburn for Summon Ice Beast, they are quite strong. Choose a big strong melee brute like a brown bear for the ice beast. Complete Mage has a reserve feat to summon weak elementals at will, might want that to further your summoning pool.
If Dragon Compendium or the Dragon magazines are open, there are some VERY powerful feats for a dual caster, let me know if those are part of your "book" collection.
Back to Arcane Heirophant, the class merges your animal companion and familiar into one, bonuses largely stacking and bad stuff going away. For example, if it dies, you can summon a new one in 24 hours for no gold cost and no lost xp. Obviously, to make use of this, you would want Obtain Familiar feat if you chose Rapid Summoning. Class gives full dual casting, druid skills, AND stacks for wildshaping. Gives some other goodies, too.
Final note, as a summoner, in general it's nice to have someone like a bard to buff your "army," if possible. The effects can really be magnified if you have lots of beasties roaming about.[/sblock]
I was basically just describing what my friend did, sorry if it's too specific for what you want. Though that build mostly optimizes summoning and doesn't hurt your ability to blast terribly much, so it's pretty good.
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