I feel that my professional exposure has been biased towards Visio, by the choice of IT managers and project managers. I've worked only in Microsoft solution centric shops where MS Office was the standard.
Are there any other professional shops out there using other tools?
I either use my whiteboard, or a nifty little Free Software tool called UMLPad.
It would be really nifty if there was a nice standard vector drawing file format so that these tools could interoperate. SVG is close, but IE doesn't support it. In the meantime UMLPad does what I need.
UModel is a very good diagramming tool which I prefer greatly over Visio.
Rational Rose is another major player in the diagramming and modeling world.
Both of these products above generally will be more expensive than Visio, making them not as widely used in all software development circles. There are also lots of smaller and pretty popular free alternatives out there like UMLPad.
Visio is only the most widely used because it is the one people tend to gravitate towards through their Microsoft Office familiarity, not generally because it's the best product out there (far from it in my opinion). I wouldn't call it a standard other than maybe a de facto standard due to its high numbers.
Yes, Enterprise Architect by Sparx Systems is very popular. I have used it at several places I have worked.
Well the current star product for user interface prototyping is Balsamiq Mockups:
http://balsamiq.com/products/mockups
Another new and good choice is FlairBuilder:
Another similar tool is ForeUI:
I've used Smartdraw during my college time and I really like it,but at the company I work we use all Microsoft stuff.
Assuming you're talking about UML diagrams, I've not worked professionally with any, but I find different free diagramming are good for different diagrams.
I prefer ArgoUML for class diagrams, sequence diagrams UMLet for deployment and component diagrams Dia for activity diagrams
That covers the diagrams I spend most of my time drawing.
I find UMLet and Dia are easy to use and put together nearly all diagrams I'd need, and ArgoUML has additional features that help with specific diagrams, and also provides code generation from class diagrams.
I've also used Borland Together, and also it's round robin features are nice, I found it really hard to work with unless you used it the way the Borland intended you, which often becomes fustrating
You might want to try Lovely Charts, if your doing something pretty light weight, their free version might work out for you.
For flow charts, I love bubbl.us
Both of these are in flash.