Peter Krenesky, from the Open Source Lab at Oregon State University, has verified that CUPS is installable and works on the XO over a traditional wireless network with the following steps from the Terminal activity:
su - yum install cups.i386
Yum currently fails in 8.2 builds. This is covered in | Trac ticket 8125. There is a workaround there too. Sometimes repeating the command a second time will work.
Configure your printer (in terminal)
Configure your printer by editing:
Example entry in printers.conf
<Printer fooprinter> DeviceURI ipp://220.127.116.11 </Printer>
/sbin/service cups start
Configure CUPS using CUPS' html interface
Rather than editing printer.conf, a full featured visual admin tool is available. In Browse open 'http://localhost:631/admin/ You will be prompted for a username and password when you try to save. I enabled root by typing the following at the command prompt (terminal): sudo passwd root and then typed the password twice, as prompted. This allowed me to use the username root and the password I choose at the prompt in the CUPS interface.
Print using the lpr command
lpr -P fooprinter foodoc.ps
(In the above example, the printer name is "fooprinter" and the document being printed is "foodoc.ps".)
The long-term plan is a Sugar integration, but in a pinch this should get you started. Of course, the option remains to copy your files to a USB stick and print from another machines.
Print from Firefox
One Sugar activity with printer support is Firefox. This has a traditional menu system. This will give you an example of printing integrated with an activity. File/Print/ brings up a traditional print dialog.