People don't think about the druid as a front-line fighter, but in fact the druid can be the best fighter among the spellcasting classes, and a contender among the straight warrior-types. With the right strategies, the druid can stand toe-to-toe with the toughest monsters -- the trick is to use the right druid spells (and your animal companion) to good effect.
Start with what may just be the most potent first level spell in the game: Shillelagh. Normally, a quarterstaff sized for a medium character does 1d6/1d6, or 3.5 points of damage per end. With a Shillelagh spell, the double weapon becomes +1/+1 and does 2d6+1/2d6+1 damage, or 8.0 points of damage per end, a bonus of +4.5 damage over the mundane staff. If you hit twice per round, the spell inflicts 9 points of extra damage per round, and if you cast it at the start of a long battle, this one first level spell inflicts 90 hp of damage per minute for one minute per level. Okay, so the chance of being in a fight in which you stand still and swing your staff, hitting twice a round for minute after minute, is pretty rare. But it still blows the Magic Weapon spell away, and on a spell for spell basis, beats Magic Missile too.
Compared with other melee weapon options, this spell makes a humble quarterstaff into the best double weapon in the game. An orcish double axe, a dire flail, and a two-bladed sword all do 1d8/1d8 vs the shillelagh's 2d6/2d6, and no exotic weapon proficiency is needed to use the quarterstaff. In fact, if you really want to be a double-weapon fighter, you may find it worthwhile to take a couple levels of druid just for this spell (healing spells, an animal companion, and druid wands and scrolls are nice extras too).
But this strategy absolutely requires two-weapon fighting. In the 3.5 version of the rules, that means the Two-Weapon Fighting feat. There are two ways to get this -- use a normal feat slot, gained at first level and every third level, or use a bonus feat from another class.
Multiclassing as a fighter is a pretty good idea for the druid who wants to fight on the front line. At levels 1 and 2, you get a bonus feat, and if you stick it out to level 4, you get Weapon Specialization as well. Feats to consider include Two-Weapon Fighting (of course), Weapon Focus (staff), Two-Weapon Defense. Later in your career, look for Improved and Greater Two-Weapon Fighting, Greater Weapon Focus, Improved Critical, and Greater Weapon Specialization. If you keep your druid levels equal to your fighter levels, then any race is an options -- but avoid the smaller ones (gnome and halfling), since your staff damage is not as good. In fact, if you have the option, a large-size liontaur is a great choice, since your staff damage is 3d6/3d6 at that size. If you just want to dip for a few levels of fighter or druid, then consider being a human, half-elf, or dwarf, because those races have a favored class option that will save you from the standard xp penalty for uneven progression.
But what if you do not have the the required Dexterity for two-weapon fighting? A ranger can fight with two weapons even with a low Dex. Even if you do have a good Dex, you may want to consider taking a couple levels of ranger. They gain two-weapon fighting as a bonus feat at level 2, and there are many other synergies to consider: skills that overlap with druid skills, levels that stack for improving an animal companion, similar stacking for the Wild Empathy class ability, and Track as a bonus feat. If you are just creating a character, consider taking ranger at first level -- the extra skill ranks pay off best then. And if you want a liontaur druid/ranger with just a two-level dip, that works out fine if ranger is a favored class for the liontaur rules you are using.
In fact, the Fighter2/Ranger2/DruidX combination may be the best one for a fighting druid. But you have to be a human or half-elf to beat the xp penalties.
What about your animal companion? Sure, it's swell if your friend is a good fighter in his own right, but the focus here is on you! So train your animal to flank your foes in battle, for that extra +2 flanking bonus to hit! A flying friend may be a better choice for flying over and behind foes without provoking attacks of opportunity. The Aid Another action might also be a worthwhile trick for your fighting friend, although the "wizards" at WotC nerfed it under 3.5 so that it only applies to one attack, not to all the attacks in a round.
Of course, the druid is a spell caster. So what about the spells besides Shillelagh? The key here is longer-duration buff spells. Anything you can cast before combat is best, since any round of combat you spend casting is a round you are not hurting the enemy. Spells to keep in mind include Longstrider; Barkskin; Bear's Endurance, Bull's Strength, and Cat's Grace; Resist Energy and Protection from Energy; Air Walk; Freedom of Movement; Stoneskin; and Ironwood (used for better armor), to name the low- to mid-level buffs.
But what about the lowly Shillelagh? At higher levels, when characters get their hands on magical weapons, a +1/+1 flaming double sword, for example, beats your Shillelagh. And your beloved first level spell only applies to a nonmagic staff, so you can't cast it on your own flaming staff to boost the base damage. Well, it seems to me that if Magic Fang leads to Greater Magic Fang, and Magic Weapon leads to Greater Magic Weapon, then Shillelagh should lead to Greater Shillelagh. Here's how I would put such a spell together:
Level: Drd 4
Components: V, S, DF
Casting Time: 1 standard action
Target: One touched oak club or quarterstaff
Duration: 1 hour per level
Saving Throw: Will negates (object)
Spell Resistance: Yes (object)
This spell functions like Shillelagh, except that it gives the touched weapon an enhancement bonus on attack and damage rolls of +1 per four caster levels (maximum +5). This spell can be cast on either a magical or nonmagical oak club or staff; if cast on a magic weapon, the enhancement bonuses do not stack.