(Please excuse the gushing... I'm quite fond of CMG Products...

)
Creative Mountain Games has quite a few nifty little items online. Mark, the head honcho there has released several "generators" that are marvelous for ingame or pregame usage. The Unlimited Titles Generator creates a stack of books for you to place in a library, give to players, or even base adventures off of--the possibilites are quite numerous. Even more useful in game is the "dwellings" generator which can generate just about any kind of home for in game usage.
Though not technically "electronic" you also might want to invest in a nice copy of the SRD for your computer. A good one, if you can find one, will be nicely formatted and bookmarked up to whazoo so you can just look at the table of contents, click the item you want and WHAM, instantly you're there with the info at your fingertips.
It just so happens I own one of these products!
The CMG Plexus SRD Revised Bundle has just about everything you need. It has the full 3.5 SRD nicely indexed and formatted well for computer, laptop, or even PocketPC usage (a tad slow on a PPC, but...any PDF is slow on PPC). In addition to the SRD, it also has packs of spells for each of the spellcasting classes. The spells are listed by level AND alphabetically, and are also fully indexed and bookmarked.
See the link in my profile (or here too, I suppose) to get over to
Creative Mountain Games