For simple sharing of directories, I use Samba. A couple of pointers:
Samba client is the package that enables you to browse shares on other computers.
Samba server is the package that enables you to make shares on a Linux computer available to be browsed. Many distros come with Samba client installed, but may not have Samba server installed. Check your package manager to find out.
The directories to be shared must be configured as "shared" in the directory permissions, as well as being named in the Samba configuration file (/etc/samba/smb.conf).
Sharing directories with that stupid Windows "homegroup" thingee works only with other Windows machines. Use so-called "simple sharing" instead.
The first time I set up Samba server, it took me about a week of poking at it on evenings and weekends; it was worth the effort, not only because of what I was able to do, but also because of what I learned along the way.
The most useful reference I found was Samba by Example
. There's a PDF here