In recent WotC sourcebooks, such as Spell Compendium and Player's Handbook II, there's been a proliferation of low-level spells that can be cast as a swift action and that have 1 round duration or apply a single small bonus to the next action. For instance, swift expeditious retreat, which is the same as expeditious retreat, except for casting time and duration.
In general, these spells are of use only to high-level casters, who can afford to spend low-level slots on minor effects if they can cast them at no cost.
However, for anyone else who's counting their slots, you're not going to load up on these slots. For example, there's a 2nd level swift spell in PHII that grants a small insight bonus on attacks. I think that I'd generally prefer true strike, which is a level lower, costs a standard action, but grants +20 and negates cover and concealment, if I'm going to spend a slot on an attack enhancement.
(Aside: the proliferation of swift spells is a reaction to the increasing offensive emphasis and capabilities of the game, which shortens combats and makes it more crucial to punch harder faster: You don't have time to wait an entire round to get your attack off. The game needs to back off this trend a lot.)
I'm inclined to introduce the following feat:
Swift Spell [Metamagic]
You cast a short-duration spell as a swift action, but it only lasts one round.
Benefit: You can apply this feat to any spell that has a casting time of 1 standard action and a duration of 1 round per level. When you cast this spell as a swift spell, its casting time becomes 1 swift action and its duration becomes one round. A swift spell uses a slot of the spell's normal level.
Special: You should use the house rule that spontaneous casters can use metamagic feats that reduce casting time normally.
Then we can take all the proliferating swift spells, assume they've had the Swift Spell feat applied, and back out the implied basis spell, to give something that's actually useful for low-level and medium-level casters.
If you ask me, I'd say that the notion of swift actions (and the spells, feats and class abilities that take advantage of them) is part of WotC's rush to emulate MMORPGs.
What is next WoTC, introducing something as annoying as Celerity 8 and 4 blood points spent in it? Honestly, you want to give a Vampire storyteller a migraine? Coordinate it so that you have Celerity 8 (thus being 5th Generation) and up against several 6th-7th Gen Vamps with equally high Celerity... let the blood spending commence. When the fact that 1 round of combat is about to be host to the following sequence; Attack, Dodge, Attack, Dodge, Attack, Dodge, Attack, Dodge, Attack, Die, Attack, Dodge, Soak.... they start to develope a twitch if you can make the combat go into round 2.
I do remember the most entertaining 'Party Vs. Dragon' fight we had, even if my players felt gipped when the Red Dragon dug out the three things in the treasure trove (rolled it ahead of time) and used them against the party... I have never seen a Mage so unhappy to see a Staff of Power before... or a Cleric to realize that the Rod the dragon just hefted was a Rod containing various Healing spells... or the party to see the Dragon smile and brandish a scroll of Wail of the Bainshee...
Hint to DM's out there, fast combat is good if the combat is getting in the way of story; if your idea of story is combat (I pity you so) then get creative... if they are going to loot a ring of invisibility off of that Ogre, make the Ogre use it!