You can also check out Nevron Draw. It's an affordable Visio alternative that lets you create different types of diagrams and comes with a lot of predefined shapes and diagram templates. Animations are not yet supported, though.

For sequence diagrams I recommend http://sequencediagram.org clean and fast to work with, it is a free online tool

I very highly recommend StarUML, I used it in college for a Software Arch. class and it's the best I've found specifically for software diagramming. Has lots of different types of diagrams built in and recently featured a redesign based on the Brackets editor.

A close second would definitely be Visio.

Glifffy diagrams is a good light weight progressive web app . Plus is super easy to use

I use LucidChart which is a cheaper version of Visio. Not sure about animation though

If you're willing to use HTML syntax, you can design something pretty close using http://angularplasmid.vixis.com. It's free, open-source, and comes with plenty of examples of how to create what you're expecting for. See below for examples:

Microsoft visio is pretty good

I'm not much of a presentation guy, so I don't know what works and what not. But I know my partner like this when he does presentations https://prezi.com and it has a lot of opportunities for animations, the drawback can come when it's about diagrams.

"yed" works for me for uml I use staruml. and for general architectural concepts I like gliffy. I found a cool mindmapping tool called coggle for general concept abstractions. :)

Great question every great software engineer and especially software architect asks at least once.

First of all, you will never going to put 150 blocks in the presentation. Make sure everything is big enough and contains the main parts and logic only, you don't need to describe every block on slides themselves.

I would recommend to watch this awesome video from the David Brown's presentation about the Software Architecture vs Code to see what diagrams he puts on slides and how.

Now some tools:

• Textografo - Diagrams from text, Online SaaS, Presentation Mode, Animations
• XMind - The Most Popular Mind Mapping Tool on the Planet, it really is amazing. I am not sure there are any animations available somehow, but you can draw large diagrams and during presentation using hotkeys easily hide/show branches.
• draw.io - this is one of my main tools, easy to use, share and contribute using Google Drive. Didn't seen animations there. Totally replaced Dia for me. You can use it for free so far you don't have many diagrams.

P.S. may be you could also add a "System Architecture" tag to this question.

I've always used Dia, which I get from the Debian repositories. The first link that comes up for dia when you google it though is sourceforge, and last I heard they were bundling junkware with abandoned projects.

Draw.io is nice too.

My two tools of choice when it comes to diagram are

• Omnigraffle whenever I need more freedom and layers to easily show/hide stuff
• Visual Paradigm when it's more technical. All my sequence diagrams for instance are done with either a whiteboard of Visual Paradigm, really great as soon as it becomes complex.

And I'm always interested in learning about better tools, hence I'm eager to read the other answers! (Many people like Lucidchart, which you might give a try, although in my use-cases, it's kind of in-between Omnigraffle and VP)