A marvellous organisation that is trying to place all Pub Dom / otherwise legally available works into a digital form for free access to anyone with a means of downloading and reading them.
(The T1 is compatible for wifi downloads by the way...)
Think that's about it.
The founder, Michael Hart, sadly died last year, September/October I think, but his work continues.
Many works are in the "first edition" form i.e. basically like photographs, if you like, of the original, which adds a lot of charm and authenticity to them, and I've spent many an hour delving through the most obscure titles, finding some fascinating tracts.
Others are proof-read and re-formatted.
MobileRead Forums also offer a similar free facility, and here most versions have been proof-read and formatted, by members, usually producing far better ones than the originals, and, again, some delightful discoveries - for example, as well as as an excellent omnibus version of Sherlock Homes, the same "compiler" has produced the definitive collection of the "Thorndyke" forensic detective works - a completely new one on me, and if you like Holmes, I think Thorndyke is a pleasant surprise!
Again, all are for free access.
There are a few other "free" legal resources, but these two are the best ones I know of.