As of firmware 2.2.0, the Touch, Glo and Mini support series information. This is shown in the library lists on a separate line for each book. As an example, the book listing will now have:
Orson Scott Card
Ender's Game - 1
For kepubs, the series information will be populated by Kobo from their server. Not all books have it yet, but they are fixing it.
For sideloaded books, the device can't read the series information. Calibre will put the series information in ePubs, but this is not part of the ePub standard, so the device doesn't read it. And other book formats do not have the information at all.
To solve this, Calibre version 0.9.8 has an updated KoboTouch driver that can set the series information. There is a new option in the configuration to enable this. If you want to set series information, open the configuration an check "Set Series information". The next time you connect the device, the driver will update the series information for all the books on the device that are in the calibre library.
Because of the way the Kobo devices handle sideloaded books, setting the series information is a little different. The Kobo devices process sideloaded books the first time they are seen. The information about the books is put into a database on the device. The device reads this database to list the books on the screen. The database contains things like the title, author, description and size. It now has series information.
For the driver to put the series information into the database on the device, the device must already have processed the book and have the details in the database. Once this is done, the driver can update the series information. What this means, is that the driver cannot set the series information when the book is first sent to the device. It can only be set the next time the device is connected.
Setting the series information will add time to the sync with calibre. The first time it is done, it could take a long time. After that, it should not affect the sync time unless a lot of books are added or have their series changed. I have done what I can to make it run as fast as possible. For two or three hundred books, it should be fast. But, for larger libraries on the device, it will probably take a few minutes.