Microsoft opens .NET source code. Ok, it would have been even better if it had been an open source license right away (and with GPL they could have even protected themselves), but hey, this variant is not uncool either - co-licensing of patents for the reference sources is already a good move. And Mono has gained a bit more security.
mono
Cloud Storage Programming Interface - Store everything. This looks quite interesting - a C# library for accessing various cloud storage. It also supports Dropbox and, most importantly, it supports Mono for Android and MonoTouch, which I could use as a basis to rewrite my small Android project in C# for testing.
F# and MonoGame on the Mac. If you want to build games on the Mac, you have an interesting option with MonoGames. This is a reimplementation of the Microsoft XNA APIs. So basically, it's just the continuation of Mono into the gaming area. Pretty cool stuff - and because a cool thing alone isn't enough, the linked article provides the whole thing with integration in F#, the functional language for .NET from Microsoft. Unfortunately, for iOS, MonoTouch and for Android, MonoDroid are required, which means there is a slight hurdle to overcome in terms of acquisition (the licenses are not exactly cheap, so maybe not quite the knockout for hobbyists).
mono/xwt. Maybe I should take a look at this high-level GUI toolkit for Mono, which, in addition to a GTK backend on the Mac, also has a Cocoa backend. With this, you can program across platforms without having to pay the look-and-feel penalty of GTK (which is simply ugly on OSX).
BOO - Getting Started. After a long time, I took another look at Boo and I like what's happening there. Still very strongly based on Python in terms of syntax, but semantically quite different - for example, real macros in various variations, so that there is really an extended syntax. Or also the optionally available Duck Typing - a variant that I particularly like, because Boo combines static typing, type inference and Duck Typing in a way that really keeps all options open for the programmer. Then there's the good integration with .Net and C# assemblies. I think I need to play around with it a bit more, because as a prototyping language it could be quite practical - and at the moment I tend to use Mono more as a runtime, primarily because of the JIT implementations available there (and with Mono also AOT compilation, where it is needed).
Phalanger 3.0 | PHP compiler for .NET. Hmm, completely passed me by - there is a PHP compiler for .NET, which makes PHP a fully integrated .NET language. And this also runs with Mono. And it's so complete that you can run a current Wordpress under mod-mono with it - and according to benchmarks, the performance goes up significantly. Maybe I'll take a look at it in a quiet hour.
Responsive Applications - Mono. An article about the different ways to build applications with GTK# so that they respond quickly and do not block the user interface, even though GTK# is single-threaded (i.e., the UI can only be accessed by the GTK# thread).
MonoMac and XCode 4
Ouch, that really got me - I wanted to play with the GUI tools, but MonoMac doesn't fully support XCode 4 yet and only has this to say:
Developers that use Interface Builder are recommended to install Xcode 3.2.6 for the time being. MonoTouch News.
The bad part: that's from March. That's way too long without support, so MonoMac is just half a tool (if at all). Running XCode 3 and XCode 4 in parallel is also not an option (both want to be in the same folder). De facto, you're either stuck with XCode 3, or MonoMac is out. Or you build your GUI with GTK# - then XCode doesn't matter (the compiler part of XCode 4 is supported), but then you can forget about the AppStore (and GTK# doesn't really look great). Damn.
MonoMac - Mono. Let's take a closer look, it now has a more up-to-date packager that includes all the Mono stuff directly into the application. On the one hand, you can then upload apps to the AppStore, on the other hand, it's simply easier to install the applications. And since I have to deal with all the .NET stuff anyway, I can also put it to good use.
IKVM.NET Home Page provides a Java VM in .NET - you should even be able to do crazy things like running Scala 2.8 on .NET with it.
Installing and using F# in MonoDevelop - a bit further down under "Installation Instructions" and look for the description for installing the F# MonoDevelop Plugin. Unfortunately, there are currently only templates for console projects with F# in the plugin.
F# cross-platform packages and samples - just look for the Mac Installer packages there (as of November 2010 Update) or above under "Download" (the link probably changes often when new releases come out). It's a simple Mac Installer, after which you have F# (OCaml for .Net) installed.
MonoMac - Mono. Ha ha, devil's tool and sell my soul and all that, but since I need C# for work anyway, I might as well take a look at MonoDevelop and its OSX integration - if I build small tools with it, I practice C# and can use it directly at the same time.
F# in MonoDevelop and cross-platform web sites & screencasts | Blog | TomasP.Net contains a lot of information about F# on Mono for Linux and OSX.
jacksonh's manos at master - GitHub - Web framework for C# that also runs with Mono. Yes, I know, C# - but I need it for the company anyway and then I could just as well take a look at something like this.