Sun Blade 2000 I'm actually planning to put an SSD in it, but my co-workers say it's a waste of money. That may be true, but it'll be the coolest Blade 2000 out there.
On a tangentially related note, a friend of mine is planning on putting an SSD into his PowerBook G4. Of course, those plans may be on hold as he claims to not use his computer much anymore, after getting an iPad.
Re: Ask HN: What is the oldest computer that you still use for production?
#81Cheaper alternative to SSD:
Compact Flash card with an adapter. I'm currently working on installing one into my iBook G4.