• Programmable Memory Sticks.  These are special copy protected red/pink memory sticks from Sony, that are different from Aibo-Life, Hello-Aibo, Pal-SE & other Sony Aiboware.  Purple, blue or white memsticks cannot be used in the 2xx/3xx series Aibo's.  8MB memsticks only work on the 210/220/310.   16MB memsticks work on all AIBO models (210/220/310/7).  They originally sold for $39, but Sony unfortunately no longer carries them.

If you own a Sony Clie, you should checkout StikZip from Aibopet.   Highly recommended.

• Sony brand Memory Stick Reader.   You need to be able to access memory sticks from your PC to initialize the RCode software.  You can also use this to backup your Aibo-Life / Hello-Aibo memory sticks (HIGHLY recommended).   I do NOT recommend non-Sony readers, since corruption of the special copy protection is known to occur.
  

Cost: $30

• Programmable Memory Sticks.  These are special copy protected red/pink memory sticks from Sony, that are different from Aibo-Life, Hello-Aibo, Pal-SE & other Sony Aiboware.  Purple, blue or white memsticks cannot be used in the 2xx/3xx series Aibo's.  8MB memsticks only work on the 210/220/310.   16MB memsticks work on all AIBO models (210/220/310/7).  They originally sold for $39, but Sony unfortunately no longer carries them.

If  you own a Sony Clie, you should checkout StikZip from Aibopet.   Highly recommended.

• Sony brand Memory Stick Reader.   You need access to memory sticks from your PC to initialize the RCode software.  You can also use a reader to backup your Aibo-Life / Hello-Aibo memory sticks (HIGHLY recommended).   I do NOT recommend non-Sony readers, since corruption of the special copy protection is known to occur.

Cost: $30

• AIBO Wireless Network Adapter, and a corresponding wireless network adapter for your PC.   These are expensive accessories for the ERS 210/220, but make development MUCH easier and faster.  The ERS-7 has WLAN built in.   Sony no longer sells the ERS 210/220 AIBO WLAN cards, but they can occasionally be found on eBay.   For your PC, several cheap brands are available.
  

Cost: ~$100 for ERS-210/220.   Already built-in w/ERS-7.   $15-$100 for PC. 

The easy way to start learning is AiboPet's YART editor.   Create simple AIBO personalities using mouse drag-n-drop techniques.  As you become more comfortable, try adding custom sound files or custom skits made using Skitter.  YART hides the gory details.  You can create new YART personalities from scratch using AiboPet's RCodePlus, or YART can tweak-up DogsLife.

Eventually, try editing the RCode directly for more complex AIBO behavior.  Use Aibnet to help verify & download hand-written RCode.  This is how DogsLife is currently developed (and why Aibnet & Skitter exist).  :-)

• AiboPet's YART Editor.  Good for beginners.  Very easy way to create simple AIBO personalities, using drag & drop techniques.  Programming experience not required, but helpful.

Cost: FREE!

• AiboPet's Performance Editor.   Great tool with a large library of dance moves built in.  Supports all AIBO models (110,210,220,310 & 7).  Contains motion & LED editors (but no sound editors).  Can be used instead of Master Studio Action Composer.

Cost: FREE!

• Aibnet.  A telnet console for communicating with AIBO over WLAN (a wireless network).  A full replacement for the Master Studio Behavior Arranger wireless console.

Cost: FREE!

• Skitter Performance Editor.   Supports ALL AIBO Models (110,210,220,310 & 7).  Contains motion editor, LED editor, MIDI & Wave sound editors, support for initializing memory sticks, testing actions on AIBO over WLAN, and several special effects/wizards.  Recommended replacement for Master Studio Action Composer.

Cost: FREE!