The AT89C55 has been replaced by AT89C55WD, which AFAIK differs only by the extra watchdog (maybe also the programming - I don;t have access to the datasheets right now). So much about it being obsolete. Nevertheless, building a programmer for one chip is... ehm... well, for a hobbyist, may be a kind of a challenge.
There is no magic in it. The only requirement is to provide decent stable Vcc (5V) source, reasonably decoupled. The "high voltage" is only an "unlock" feature, so there is no significant current drawn from it.
Then, it is only a matter of properly applied digital signals (>20) in a given sequence - see datasheet. The only problem is to keep the given timing of programming pulse - this is not trivial to achieve on PC, especially in multitasking environment. Monostable flip-flops, or microcontrollers (see given links - and see also Peter Dannegger's site, if I recall it right) can be used to achieve this, if there is no full control over the PC's resources.

An example of a purely PC-controlled (with SW in DOS) LPT-connected "minimal" design is here:
http://www.mcu.cz/modules/n...storyid=99 . Don't be worried by the czech text, it basically says that it is downloaded from a chinese site which no longer exists. The sw might be not available due to recent server crash: if you are seriously interested, drop me an email, I can try to dig it out.

But, as most of the posters stated here, it is questionable if it is worth the effort.

Jan Waclawek