You can find an assortment of tools & examples to get you started programming your PS2 here. If you develop something yourself be sure to add it here.

"In software, a toolchain is the set of computer programs (tools) that are used to create a product (typically another computer program or system of programs). The tools may be used in a chain, so that the output of each tool becomes the input for the next, but the term is used widely to refer to any set of linked development tools." - wikipedia

ps2toolchain-20070626.tar.bz2
precompiled toolchain for windows
EE/IOP/DVP compilers for Win32

misc tools.

Rad Host Client 1.8a
VCL Vector Unit Preprocessor
PS2MENU
OpenVCL v0.3.3
CD-Tool
PS2 BootAdvance
PS2Desktop
PS2Reality Mediaplayer 1.50
Inline mod converter (mod2c)
Bios dump util

misc packers and unpackers.

PS2-Packer 0.4.4
SjCRUNCH v2.1 - PS2 ELF Packer
ps2unpack ( unpacks OSDSYS, Win32 exe )

misc debuggers, disasm.

Win32 Cygwin Remote GDB, test release
ps2reg 1.1
PS2DIS - Hanimar's disasembler

Misc image/texture/icon utilities.

MC ICON.SYS Generator
PS2 Image Studio -by:Lion
MilkShape plug-in: Icon Importer/Exporter v0.8
bmp2icon v0.2