I dusted off my old DLink DI 624S "Wireless Storage Router" which has 2 USB ports that can be connected to USB hard drives. Most importantly this device has file server software embedded in it.
I plugged a mini SD card reader into one USB port and the portable HDD into the other. I then connected to the router (via WiFi), both drives were then visible in FileBrowser (after adding the router to it) making it possible to backup photos from the SD card to the HDD. I can also use FileBrowser to view any of the photos on the HDD while traveling.
The router is also useful as a wireless hotspot if you find yourself in a hotel that has only Ethernet (there still seem to be some around). It's one bit of gear to pack but smaller and lighter than even a netbook.