Below is only a sample of the dozens of products available, that you can use to compare features/prices. I picked products I thought were innovative or otherwise interesting, but have not tested nor can I recommend any of them.
Some cases (see below) double as stands
Case - Stands
Targus VuScape Cover & Stand for iPad 2 Case $22
Apple - Smart Cover - Cover up, stand up $39
Gilsson PU Leather Multi-Angle Adjustable Stand/Carrying Case for Apple iPad $21
Speck Products | iPad Cases | Tablet Cases | Covers for iPad
Timbuk2 Kickstand Case for the iPad - Timbuk2 Bags $49 ($29 Sierra Trading Post)
These docks keep your tablet charged and synchronized.
Galaxy TabĒ 7.0 HDMI Multi-Media Dock $43
Walmart.com: Hipstreet iPad 2 Aluminum Hard Case with Bluetooth Keyboard and Stand $50
Kensington KeyFolio Pro Performance Keyboard Case for iPad 2 Wireless Keyboard $60
Galaxy TabĒ 10.1 Keyboard Dock $80
keyboardsMust Have iPad Accessories - Bluetooth Keyboards $40-$90
Keyboards at PC Magazine
Logitech 920-003544 Fold-Up Keyboard $120
Amazon.com: Matias Folding Keyboard: Electronics $40
Amazon.com: Verbatim 97537 Wireless Bluetooth Mobile Folding Keyboard for iPhone, iPod Touch, iPad, iPad2 and Other Tablets $61
Menotek Flexible Bluetooth Waterproof Mini Keyboard $30
Amazon.com: Flexible Bluetooth/Wireless Keyboard for Apple iPad: Computers & Accessories $30
Incase Field Bag (Avail. at Apple Store Jan. 2012), similar to Kensington Sling Bag
Ipad Cases | eBags.com
Samsung Galaxy Tab (Android) The Galaxy Tabs have 1. A 30 pin multifunctional jack. 2. An 3.5-mm audio jack 3. An micro-SD card slot 4. 1.3 MP front facing camera for video calling It comes with a cable for the 30 pin port with a male usb plug for charging, syncing and accessing the SD card when connected to a computer. HDMI adapter $40 USB adapter $20 The USB adapter plugs into the 30-pin port and accepts a standard usb plug. It will read files on a flash drive, but does not have enough power to read a hard drive (HDD) without a powered hub. You need a file manager app to view files on the external device. USB Host support (and Honeycomb 3.1) is required to connect USB accessories, so a Verizon 7" tab won't work. The 7.0 Plus with 3.1 will work. See Samsung Galaxy Tab HDMI, USB and SD Card Adapters
Bluetooth AccessoriesThere are a variety bluetooth devices to use with your tablet. Keyboards (see above), headsets, barcode scanners, auto diagnostic interfaces to your car's computer.
Bluetooth headphones allow you to listen to music or talk on the phone in tablets with phone capability.
If you want to listen to music make sure the specs supoprt Advanced Audio Distribution Profile (A2DP).This profile defines how high quality audio (stereo or mono) can be streamed from one device to another over a Bluetooth connection.
Many tablets have the phone option disabled by the supplier (e.g. Verizon) so you do not need headsets with a microphone unless you are using skype, chat or something else that requires voice input.
Some people reported problems with bluetooth headphones on iPads. Mono headsets may not work with iPads. One forum post said, "you are going to find the implementation of BT very frustrating on the iPad."
Teksoft has a variety of apps for use with bluetooth keyboards, headsets and barcode scanners.
Prices range from $20 to $120 or more.
Display Interfaces - Wireless Displan (WIDI)Wireless Displan (WIDI) or Mirroring devices plug into a projector or large monitor and can mirror the display of a laptop, tablet or smartphone so you can make presentations from your own device.
Needed primarily for mobile (Android) connection. I recommend the Netgear Push2TV PTV-3000 (the model I have) Amazon.com link: www.amazon.com/NETGEAR-Push2TV-Wireless-Miracast-Certified/dp/B00904JILO/
Based on the site for the following item, 'm not sure whether a USB adapter might be a better idea:
The iOS connection depends on the regular iPhone/iPad charging cable, not a proprietary HDMI connector cable (see this Amazon precanned search: Amazon Search )
A couple of folk have suggested Chromecast as an alternate option. I've not worked with Chromecast (Frank does have a Chromecast device). ComputerWorld's 2014 review of mirroring devices states "Chromecast works with Macs, Windows PCs, iOS and Android devices, but relies on apps rather than true mirroring for most devices".
MiscellaneousMini Dual USB Port Car Charger Adapter $3.67
Amazon.com: Cocoon GRID-IT! Organizer Case, Black (CPG7BK): Computers & Accessories $10
Smart Phone Accessories:
Amazon.com: Brando Flexible Mini Capsule Microphone: Cell Phones & Accessories $20
Amazon.com: Joby JM1-01WW GripTight Mount (Black): JOBY: Cell Phones & Accessories $13