Memory Upgrades:

Palm Do it yourself memory upgrades - Lots of great information about upgrading your Palm's Memory !
http://www.interlog.com/~tcharron/Palm8M/upgradeservice.html

More Palm Do it yourself memory upgrades - Information about upgrading your Palm.
http://palmsurgery.webjump.com/palmv8.html

Palm V 8-MB Memory Upgrades ! - EFIG has suspended Palm V upgrades. They now have Springboard diagnostic cards and extender cards as well as Springboard development info.
http://www.efig.com

Homebuild 4MB memory extension for Palm III - This page describes how to perform a modification to the memory board of the Palm III to upgrade the 2mb board into 4mb !
http://bodotill.suburbia.com.au/

Port Modules:

Port Cover with Led (Talelight) - Several goodies to stick in the Palm's serial port including LED Modules, IrDA Transceivers, Vibrating Alarm modules, and more! Visit Tech Center Labs:
http://www.talestuff.com/

Power Upgrades:

External Power Plug - Another External Power Modification by Ben:
http://users.netconnect.com.au/~qeeng/

NiMH Rechargeable & Charging Cradle - Peter is using NiMH rechargeable batteries to power his Pilot & is exploring a way to convert the HotSync cradle into a charger! Visit Peter's Pilot Page:
http://www.pstec.de/ppp

Battery Drain Fix - Modify the Pilot's cradle to eliminate battery drain that occurs from leaving the Pilot in the cradle.
http://www.conklinsystems.com/pilot/drainfix.shtml

A small connector adapter that will let you leave your PalmPilot on the Cradle all day with NO BATTERY DRAIN!:
http://www.cesium.com/pilotdtr/

Battery Drain Fix using the Bridge - This modification allows you to modify the Bridge, instead of the Pilot's cradle to eliminate battery drain.
http://www.midwestpcbdesigns.com

Recharge NiMH's inside the Palm - Alberto's modification allows you recharge NiMH's inside the Palm
http://members.xoom.com/ing_varela/palmloaderengl.htm

Speaker Upgrades:

Speaker upgrade, Memory upgrades, Cradles/external power updates - Martin Research will perform upgrades on your Pilot for a fee... If you can bare to be without your Pilot for a short time, lend it to these folks for an overhaul !
http://www.teleport.com/~accbo/PalmPilot/Audio.html

Stylus & Case:

P3 'screw-apart-reset' stylus for your PalmPilot - Olger Diekstra made his own screw-apart stylus. "I already have two Grey styluses that I received when I bought the Pilot. So I creating my own screw-apart-and-reset stylus. This is how I did it: I used the two Grey styluses and cut 'em both at the appropriate length. In the bottom part I drilled a hole and carefully created the screwthread in it. On the other end I also created screwthread and inserted a (very) hot paperclip into the tip and cut off the extra piece. Off course, you need to be a bit handy and have the appropriate tools, and work carefully, but as you can see on the pic, it can be done (took me about an hour)." - Olger Diekstra
(picture)

Misc:

Voice Recording on your Palm III & V series- i-Vox adds memo recording capability to the Palm III & V series, replacing the flip-cover with a stand-alone voice recorder.
http://www.i-vox.com/

ADXL202 tilt sensor for the PalmPilot - This page describes how to add a tilt sensor to the Pilot to play Mulg II.
http://bodotill.suburbia.com.au

Color cases for your Palm ! - This company is selling replacement cases for the Palm III, IIIx, IIIe, and IIIxe in various colors !
http://www.palmcolors.com

Cradle to Modem adapter - Instructions on how to make a cradle into an external modem cable.
http://www.massena.com/darrin/pilot/luiz/item10.htm

External Audio adaptor - Instructions on how to add an external audio adaptor.
http://www.massena.com/darrin/pilot/luiz/extaudio.htm

Palm V Quick Draw Holster - Instructions on how build your own.
http://www.angelfire.com/ms/holster/holster.html