<a href="http://hem.passagen.se/flubba/gba.html" target="_blank" >FluBBa</a> has released a new Sega Master System emulator for the GBA (works on Nintendo DS and Gamecube Gameboy Player too), this release is considered beta and contains a new Rom Builder by Loopy:
Heres the release news:
V0.4 - 2005-08-10 (FluBBa)
Fixed memory management again (Shinobi, The Ninja, SDI).
Fixed a rendering bug in GG mode (GG Aleste).
Fixed sprite offset -8 (Ghouls'n Ghosts).
V0.3 - 2005-08-07 (FluBBa)
Fixed nametable switching a bit (Sylvan Tale, Road Rash).
Fixed 256x224 screen for GG games (Star Trek games).
Fixed memory management a bit (Ys, Terminator).