If you want to learn or just find out a little about F# then what could be better than an interactive website that provides a tutorial and lets you enter, edit and run code.
Microsoft's championing of F# is something that is all the more surprising after it dropped the Iron languages - IronPython and IronRuby a few months ago. But the support for F# seems strong - it gets used for projects and there are new developments all the time.
The latest is the Try F# website. This provides an interactive web based IDE that you can use to enter and run F# programs. The design of the IDE is a little confusing at first but as long as you are prepared to read the instructions and explanations in the panel to the left it all makes sense.
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If you are even more patient and persistent you can work your way though a course on simple F# - but be warned you do get to recursion, higher functions and other tough topics in only a few steps. This is not a criticism of the tutorials just a warning that F# probably isn't a good choice as a first language. The interactive course runs from the very basics of the language - e.g. syntax, indenting and so on, though objects and into parallel programming. It even covers building a UI via a Silverlight Canvas which is more than Visual Studio lets you do!
You can read the code and by clicking the Run button it is transferred to the editing window and the results of running it are shown in the output window. You can then edit the code to play with it or improve it and try it out again by clicking run. You can even save your program to a local disk and load it at a later date.
Overall this is a simple and very attractive introduction to F# - why not give it a try.
Try F# website
Guide to F#