I have just posted my Transistor Tester on:-
http://www.thebox.myzen.co.uk/Hardware/Transistor_Tester.html
This uses a robot electronics USB to I2C interface OR an Arduino along with six ICs. It is driven through a Processing application. It tells you the transistor type NPN or PNP, the gain and the transistor pin-out. I have found it most useful in determining the pin-out of all those unmarked and un-findable transistors I have acquired over the years. Hope you find it useful.
This is really cool and would be a really useful thing to have. I want to make one but I just got my arduino and have a few other projects I want to get out of the way first. Its on the list though. Maybe by then I can make it a stand alone unit like you said, with an lcd screen or something. Of course if anyone would like to beet me to it I would not mind as long as they posted the script. ;D
Nice project;
For anyone interested in how semiconductor testers were designed before the micro age I've attached a couple of pdf file links of the B&K 530 semiconductor tester. This was quite the piece of test equipment in it's day and still sells well on E-bay. Perhaps it will give someone ideas on how to expand on a Arduino semi tester.
Lefty
Parts list and schematic only:
http://bama.edebris.com/download/b&k/530rev/530rev_sch.pdf
Full manual:
http://bama.edebris.com/download/b&k/530/B&K%20530%20Semiconductor%20Tester.pdf