Overlord

Overlord is really a must have. It connects Illustrator and After Effects with each other with a magical bridge. You can send shapes back and forth with a simple click of a button. The Illustrator shapes will become AE Shapes automatically. Text will become editable text in After Effects. Just wonderful. It is the ultimate time-saver.

It is a paid plugin and it will cost you $45. It is totally worth it.

Buy now via Battle Axe

AutoFill

AutoFill is a revolutionary plugin from Plugin Everything that fluidly fills the bounds of your layer to save you hours of tedious masking & keyframing. This save so much time in animating a logo for example. And clients always love the effect. I use it a lot. It costs $49,95. Money well spent.

Buy now via Plugin Everything

Flow

Flow brings an really easy interface to After Effects for customizing animation curves without needing to touch the graph editor. It makes your animations nicer with one click of a button. I prefer the simple Flow plugin above the more complex Motion 3. Flow costs 30 bucks, but will save you so much time.

Buy now via AEscripts

Universal Audio

Universal Audio is a really handy when it comes to timing animations to voice-over, music and sounds. Make audio flow through all your comps with one button, always giving you audio reference along with markers to animate to, no matter where you are in your project. This is such a time saver when editing on a voice-over track with multiple nested compositions. You will hear the soundtrack in every comp you are working in! 10 bucks again well spent.

Buy now via AEscripts

GifGUN

GifGUN is so much fun. It's the best way to export animated gifs directly from After Effects with just one click. The produced gifs are very customizable, with easy settings. From frame rates to maximum used colors. It always delivers. Price: $29.99.

Buy now via AEScript

PS: Almost all great plug-ins and scripts for After Effects can be found on this great website: aescripts.com