How can I play .smil videos?
You will have to choose one because I haven't got much experience with it but here is a list of capable players for .smil files: http://www.w3.org/AudioVideo/#SMIL
Apparently http://www.ambulantplayer.org/ can play all the formats of smil files so I would recommend you start with this one.
You can build the source code following the instructions here.
Hf and gl ;)