ubc 48gx faq
http://www.engr.uvic.ca/~aschoorl/faq/48faq.html

 HP to PC link. 

Required Parts: 

     Soldering iron and flux 
     RS232-9 or RS232-25 shield (serial port shield) 
     RS232-9 or RS232-25 female connector (serial port connector) 
     4 pin HP connector, with sockets spaced 2 mm (NOT 0.1") apart 
     Some copper wire 

 broken floppy drive, hard drive, or CD-ROM audio cable lying around, look inside and see if you
can find a connector there that will fit the HP48. Do not use a 0.1" connector, as this will damage the pins on your calculator.


http://hp48.wsjr.com/list.htm

How to join and leave the list


access, and download, the User's Guide and the three
                     volumes of the Advanced User's Guide. 

                      HP 49G 


                     View by Chapter (Version 1.2)
                     Introduction
                     Preface (159 KB)
                     Table of Contents (30 KB)

                     Chapters
                     1. Keys (296 KB)
                     2. Basic operation (291 KB)
                     3. Creating and editing expressions
                     (116 KB)
                     4. Plotting graphs (348 KB)
                     5. Working with expressions (211 KB)
                     6. Solving equations (152 KB)
                     7. Storing objects (129 KB)
                     8. Vectors, lists, arrays, and matrices
                     (312 KB)
                     9. Using statistics (140 KB)
                     10. Introduction to programming
                     (143 KB)

                     Appendixes
                     A. Connecting to another calculator
                     (47 KB)
                     B. Error messages (38 KB)
                     C. Units (76 KB)
                     D. Troubleshooting (79 KB)
                     E: Working in PRN Mode (91 KB)

                     Index
                     D. Index (286 KB)

HP 49G AUG (Ver. 1.2)
                     Volume 1
                     View by Chapter 

                     0. Preface (49 KB)
                     1. Basic Operations (88 KB) 
                     2. System Flags (53 KB)
                     3. Editing (119 KB)
                     4. The Stack (58 KB)
                     5. Matrices/Linear Algebra (177 KB)
                     6. Unit Objects (107 KB)
                     7. Constants Library (63 KB)
                     8. Number Bases (80 KB)
                     9. Lists and Sequences (104KB)
                     10. Advanced Plotting (99 KB)
                     11. Memory (67 KB)
                     12. Date/Time Arithmetic (80 KB)
                     13. Customization (74 KB)
                     14. CAS Commands (459 KB)

                     Volume 2 -- Other Commands
                     Commands A-F (765 KB)
                     Commands G-P (665 KB)
                     Commands Q-Z (859 KB)

http://www.hp.com/calculators/techsupport/graphing/49g_userguide/

http://www.area48.com/news/

http://www.area48.com

http://www.hpcc.org/datafile.html