The package for lrz is called lrzsz. You should be able to find it after "opkg update". As for minicom, it is only available in the unstable feed of Ångström. If it is no problem for you to use the unstable feed you, replace all occurences of "2008" with "unstable" in /etc/opkg/*-feed.conf. Run "opkg update" and "opkg upgrade" to upgrade to the unstable version of Ångström. No guarantee that it will work flawlessly.

Maybe you can only install the wanted packages from the unstable feed, i.e. "opkg install http://www.angstrom-distribution.org/feeds/unstable/ipk/glibc/armv5te/base/minicom_2.3-r0.5_armv5te.ipk" without completely upgrading to unstable, but there might be dependency resolution problems. If that is all not an option, you can also setup the OpenEmbedded build system as described in our LinuxGuide and compile the packages yourself, although this can take some time.

I had a problem like this too. There's a small terminal emulator embedded in BusyBox... just type microcom... it may be all you need.

Peter