These are some common libraries I use in my code.
All C libraries are vb6 compatiable (stdcall)
pe_lib - vb6 ActiveX DLL
PE file format parsing code
proc_lib - vb6 ActiveX DLL
Process Enumeration/Manipulation
globals - vb6 Activex DLL
Global Multiuse class with common lib functions
olly_dll - C DLL
ASM/DISASM engine
GPL Copyright (C) 2001 Oleh Yuschuk
hooklib - C DLL
Detours style hooking engine
extended version of Daniel Pistelli's ntcore.com hook engine
zlib - C DLL
ZLIB compression library - win2k+ compatiable
Jean-loup Gailly & Mark Adler