I think that wireless is the answer to the iPad lack of physical connectivity. Without purchasing any hardware or software there are quite a few Cloud storage options.
If, like me, you want to use your own hardware, some options that I have found (that don't require jail breaking) are described below. I would much prefer that the iPad had a fully functional USB port, SD card slot and access to the file system. I will certainly be taking this into consideration next tine around.
You can get reasonably good access (over WiFi) to files on fileshares with an app called FileBrowser.
Once you have located the file, using the file manager/finder style interface, you can usually view it in FileBrowser or choose "Open in GoodReader" and store it in the GoodReader file system. I have lots of documents (PDF, Word, images) stored and ready to access in GoodReader.
Fileshares can be set up on most network drives (I have a Western Digital NAS) using the browser based management tools that usually comes with them. Some fileshares are often setup by default such as "Public", "usb1" etc.
My NAS has a USB port and, if I plug a mini SD card reader into it, I can access photos on my camera card. FileBrowser has a reasonable SlideShow viewer built in.
My HP AirPrint printer has an SD card slot and I can also access SD cards plugged into it, using an automatically created fileshare.
Lastly, I have experimented recently with a "plug computer", a small Linux box with lots of input/output options such as 2 x USB, 1 x SD, 1 x eSATA and 2 x Ethernet. With an App called iSSH and knowledge of some basic Linux commands, you can copy files just about anywhere you want using the iPad as a console.