Installing mono 1.9
To run the most recent libsecondlife release you need to have at least mono 1.9 installed. the following step-by-step recipe applies to a ubuntu 7.10 system and you should be root:
installing pre-reqs
apt-get install build-essential bison gawk apt-get install libglib2.0-dev apt-get install libpng12-dev libx11-dev libfontconfig1-dev apt-get install libfreetype6-dev libjpeg62-dev libtiff4-dev apt-get install libungif4-dev libexif-dev libcairo2-dev apt-get install libpango1.0-dev libgtk2.0-dev libglade2-dev apt-get install libgnome2-dev libgnomecanvas2-dev libgnomeui-dev apt-get install libgnomeprint2.2-dev libgnomeprintui2.2-dev apt-get install libpanel-applet2-dev libgtksourceview-dev apt-get install libgtkhtml3.14-dev
installing libgdiplus
Pour des raisons de configuration w get est écrit avec un espace, il faut bien entendu supprimé cet espace pour obtenir la bonne commande.
w get http://go-mono.com/sources/libgdiplus/libgdiplus-1.9.tar.bz2 tar xvf libgdiplus-1.9.tar.bz2 cd libgdiplus-1.9 ./configure --prefix=/usr/local make make install
installing mono
w get http://go-mono.com/sources/mono/mono-1.9.tar.bz2 tar xvf mono-1.9.tar.bz2 cd mono-1.9 ./configure --prefix=/usr/local make make install
installing nant
w get http://switch.dl.sourceforge.net/sourceforge/nant/nant-0.86-beta1-src.tar.gz tar xvf nant-0.86-beta1-src.tar.gz cd nant-0.86-beta1 make install prefix=/usr/local
you now have the base setup, which is sufficient for building and running libsecondlife and opensim. the following packages are add-ons that are nice-to-have but not necessary-to-have. i do recommend installing the monodoc & mono-tools stuff, however — it makes live easier 
gtk-sharp
w get http://go-mono.com/sources/gtk-sharp210/gtk-sharp-2.10.4.tar.bz2 tar xvf gtk-sharp-2.10.4.tar.bz2 cd gtk-sharp-2.10.4 ./configure --prefix=/usr/local make make install
gnome-sharp
w get http://go-mono.com/sources/gnome-sharp2/gnome-sharp-2.16.1.tar.gz tar xvf gnome-sharp-2.16.1.tar.gz cd gnome-sharp-2.16.1 ./configure --prefix=/usr/local make make install
gtksourceview-sharp
w get http://go-mono.com/sources/gtksourceview-sharp2/gtksourceview-sharp-2.0-0.12.tar.bz2 tar xvf gtksourceview-sharp-2.0-0.12.tar.bz2 cd gtksourceview-sharp-2.0-0.12 ./configure --prefix=/usr/local make make install
monodoc & mono-tools
to get the monodoc C# documentation viewer (recommended!) we need to install the monodoc package and the mono-tools package. monodoc itself needs to be installed inside the mono-1.9 source directory1 from above.
install monodoc
cd mono-1.9 # this is the source directory from the above w get http://go-mono.com/sources/monodoc/monodoc-1.9.zip unzip monodoc-1.9.zip cd monodoc-1.9 ./configure --prefix=/usr/local make make install cd ../..
install mono-tools
w get http://go-mono.com/sources/mono-tools/mono-tools-1.9.tar.bz2 tar xvf mono-tools-1.9.tar.bz2 cd mono-tools-1.9 ./configure --prefix=/usr/local make make install
configure will mumble about gecko-sharp.dll not being build, that's ok, just ignore it.
1.otherwise, monodoc will not pick up the C# doc for the base assemblies.