the current package list for the installed OS is here:
http://ports.ubuntu.com/dists/jaunty/main/binary-armel/Packages.gzbut you will need to parse that (eg in a text editor search for "Package: " )
You tried to download and install an intel x86 compatible package, the plug is an ARM processor, hence why you are having problems.
at present, the only libapache2-mod-* packages present are:
Line 65839: Package: libapache2-mod-auth-kerb
Line 65862: Package: libapache2-mod-auth-mysql
Line 65883: Package: libapache2-mod-auth-pam
Line 65905: Package: libapache2-mod-auth-pgsql
Line 65927: Package: libapache2-mod-auth-plain
Line 65949: Package: libapache2-mod-auth-sys-group
Line 65972: Package: libapache2-mod-macro
Line 65994: Package: libapache2-mod-perl2
Line 66022: Package: libapache2-mod-perl2-dev
Line 66049: Package: libapache2-mod-perl2-doc
Line 66074: Package: libapache2-mod-php5
Line 66112: Package: libapache2-mod-python
Line 66141: Package: libapache2-mod-python-doc
so you either need to contact the package maintainer to port it for you, or find someone else, or have a go yourself, or find another distribution that may have that ported already.
HTH