HANDHELD EMULATORS

Gameboy/Color/Super Gameboy
BGB [v1.12] (Homepage)
Gambatte [v0.3.1, Qt] (Homepage) -GB/GBC only-
KiGB [v2.04] (Homepage)
No$Gmb [v2.5] (Homepage) -Old but good, shareware-
VBA-M [v368] (Homepage)

Gameboy Advance
VBA-M [v368] (Homepage)
No$Gba [v2.6, free - v2.6a, donators] (Homepage)

Nintendo DS
No$Gba [v2.6, free - v2.6a, donators] (Homepage)
iDeaS [v1.0.2.2.] (Homepage)

WonderSwan
Cygne [v2.1a] (Homepage) -Old-
OSwan [v0.70, original] (Homepage) -Old-
OSwan [v1.73, modified] (Homepage - Japanese)

GP32
GeePee32 [v0.43] (Homepage)

Neo-Geo Pocket
NeoPop [v0.71] (Homepage)

Game Gear
Kega Fusion [v3.61] (Homapage)

UPDATE: Rewrote the list for those who find it useful. /agz

Updated the list for those who find it useful.

I would guess that there are little to no working emulators available for the PSP.

But the topic is only about handheld emulators for PC, not emulators for handhelds.

VBA-M is independent now and not 'vendorlocked' into any external sites. The old subdomain is pretty much obsolete/inactive and doesnt redirect (yet?) to the new location.

Last rev is 854, and new homepage and its official forum, so for VBA-M progress and updates, one location:
http://www.vba-m.com
http://www.vba-m.com/forum/

The above sites won't load. Was fairly curious as to the status of this emulator. Would be wonderful to know how you guys are handling the online part.

VBA-M changed hosts a good while back, after issues first with NGEmu and then the vba-m.com domain. Use Google Code if you want the latest binaries.

Does it handle any sort of linkage?

I don't remember (nor have I bothered looking, really). If VBA-M doesn't support linking, then use VBALink.