MarshallSoft Computing  
   Serial communications, email, FTP, and winsock libraries for Windows.
   http://www.marshallsoft.com/

EDSS/Models-3 I/O API  
   Provides the environmental model developer with an easy-to-learn, easy-to-use programming library for data storage and access, available from both Fortran and C.
   http://www.emc.mcnc.org/products/ioapi/

Greenleaf Software  
   Serial communications libraries, components and tools.
   http://www.gleaf.com/

DC Micro Development, Inc.  
   Cross-platform development libraries for C/C++ and Visual Basic. Products include libraries for data compression, TCP/IP protocols, dynamic html emission, and help authoring software.
   http://www.dcmicro.com/

OptiVec: Libraries for Engineering and Science  
   OptiVec offers more than 3000 Assembler-written vector, matrix and complex math functions for PC language compilers, 2-3 times faster than compiled code.
   http://www.optivec.com/

SGE  
   API that provides low level access to audio, keyboard, mouse, and display framebuffer across multiple platforms.
   http://www.etek.chalmers.se/~e8cal1/sge/

CMATH  
   Assembler written complex number math library (single, double and extended precisions), intended as a high-quality replacement for the available C++ complex class libraries, and as an add on for Pascal or Delphi.
   http://www.optivec.com/cmfuncs/

OpenML (Open Media Library)  
   A cross-platform standard programming environment for capturing, transporting, processing, displaying, and synchronizing digital media (2D and 3D graphics, audio and video processing, I/O, and networking).
   http://www.khronos.org/openml/

WCSC  
   Serial communication libraries, drivers, and DLLs for all Windows and MS DOS that include Zmodem, Xmodem, and Ymodem file transfer protocols, as well as full modem control. Nine bit and Multidrop protocol for RS232, RS485, & RS422 serial communication
   http://www.wcscnet.com/

TEC-IT Barcode DLL  
   For developers who need to integrate and print bar codes from within their application. Supports all linear bar codes including Code 39, Code128, 2of5 IL, EAN, UPC, Postnet as well as 2D-symbologies includinmg PDF417, MaxiCode and Data Matrix.
   http://www.tformer.com/barcode/go/barcode_dll_1.htm

DMM_Windows_DLL  
   A Win32 library allows to adjust shapes of windows and to work with translucence and transparency of the windows. All the functions can be combined with one another so that interesting effects in the windows can appear. [Commercial]
   http://www.dmm.cz/en/dmm_window_dll.htm

SuperCom TCP/IP  
   An optimized, thread based, Low Level Engine, which handles simultaneously connections, buffers data and generates events. Optimized threads reduce CPU load to minimum. A dual mode programming interface is provided (DLL and ActiveX). [Commercial]
   http://www.adontec.com/supert_e.htm

GET.DLL  
   A freeware maGic ExTension, a DLL, that extends the Magic RAD software (for Windows) from MSE. (A this website, you will also find other resources for Magic developers.)
   http://www.geocities.com/siliconvalley/bit/1809/

Developer City: Free Programming Resources: Libraries  
   A variety of free libraries, with or without source code, for: accessing databases (with/without ODBC, SQL), encryption, graphics/images, compression, fonts, GUI's, 3D engines, 2D engines, and sockets programming.
   http://www.thefreecountry.com/developercity/freelib.html

Nine-9s  
   Protocol stack software for telecom and data communications protocols in source code. Also video and audio codecs.
   http://www.nine-9s.com/

Cioina  
   Mathematical parser and symbolic differentiator (Windows .dll and Linux .so files), and Delphi, Kylix, C++ Builder, C#, VB using examples. [Commercial]
   http://www.geocities.com/alexei_cioina/cioinaeval.html

DllDump  
   A collection of over 700 DLL files.
   http://www.dlldump.com/

SI Grid DLL  
   A 32 bit grid control for use in Windows development. By Software Innovators. [Commercial]
   http://www.softwareinnovators.com/products.php?SM=TL&PD=SIGRID&PHPSESSID=c6edb65368133c950cde4cccfbf142de

HtmLayout  
   A small, fast embeddable HTML renderer, HTML layout manager and HTML printing DLL for Windows. [Commercial]
   http://terrainformatica.com/htmlayout/

DoneEx Software  
   Software tools for developing desktop applications, including: DoneEx AppBinder ActiveX - allows launch DOS or Win32 console programs from application and to capture the standard input and output data streams of launched program; DoneEx AppBinder DLL - he
   http://www.doneex.com/

MultiMedia SoftWare  
   32 bit DLLs for Windows: component for MS Windows Mixer controlling, component for any windows controlling. [Commercial]
   http://www.mmsw.cz/devcorner/

Hunny Software  
   MIME tool kits for C++ and Java, .Net.
   http://www.hunnysoft.com/

ConvertSpot  
   Provide COM/DLL components to convert PDF to XML, PDF to text, MS Word to text, PowerPoint to text, Excel to text, Excel to xml, Excel to CSV.
   http://www.convertspot.com

ComISDN  
   Advanced TAPI Service Provider (TSP) for COmputer Telephony Integration and IP Telephony.
   http://www.comisdn.com

SlavaSoft FastCRC Library  
   Fast, highly optimized implementation of popular checksum algorithms: CRC32, CRC16, CRC16C (CRC-CCITT). The library allows to calculate checksums for files, memory blocks, strings, streaming data. C/C++, VB examples. [Shareware]
   http://www.slavasoft.com/fastcrc/

The Dynamic Link Library  
   Collection of 36000 Windows system files like DLL, OCX, VBX, INF and SYS.
   http://www.dynamiclink.nl

ZeeGrid  
   Grid control for Win32 API programmers implemented as DLL. Nice features built-in. Column reordering, sorting, printing and exporting to comma-delimited text file to name a few.
   http://zeegrid.com/

DSX  
   Developer of ActiveX, Win32 DLL, and JavaBean tools for barcode solutions.
   http://www.dsxtech.com/

RTF-to-HTML DLL  
   DLL/COM for convert RTF and text in to HTML, XHTML format.
   http://www.sautinsoft.com/com/rtf-to-html_dll/rtf-to-html_dll.htm

Word Processing File Conversion Library  
   A library of DLLs which can be called from any Windows application. Contains functions to convert documents between different Word Processor file formats, and to read or write formatted text to or from word processor file formats.
   http://www.doc-api.com/