apt-cache search enet physfs
sudo apt-get install libenet-dev libphysfs-dev
( Will provide libenet0debian1 = 1.2.1-1
and libphysfs1 = 2.0.0-4 )
......
P.S. : There are also the two 'Search' windows in Synaptic ...
and of course the online "Search window" :
http://packages.ubuntu.com/lucid/libenet-dev
......