I originally started doing this job with exact audio copy years ago. EAC is free to download (
http://www.exactaudiocopy.de/) and is my default ripper when all else fails, but is really slow. FLAC is the way to go as it is lossless and easy to associate artwork and metadata to.
Now I use a Vortexbox, which takes the pain and hassle out of ripping, tagging and sorting out artwork. This is similar to what I use
http://www.vortexbox.co.uk/VB_Essential ... 16227.aspx. The kids and I took about five weeks to rip 2000 odd CDs to the machine. We simply left a pile of CDs next to the machine and let the kids get on with it (in return for suitable payment). You can set it up to mirror the FLACs to MP3, but we don't bother. It also works as a NAS drive, or you can play from it via usb to a suitable DAC. The Vortexbox is a stone cold bargain for what it does and is idiot-proof (as evidenced by my having had three trouble free years using mine.
If you have FLACs you can batch convert to MP3 using something like dbpoweramp. If you have MP3s you can covert to FLAC or WAV, but the converted files will be lossy (i.e. the data has been compressed).
I also use MP3tag (
http://www.mp3tag.de/en/) to sort out the metadata on files as every now and then the vortexbox can't find the data for a disc (Nearly every CD issued by The Heads needs to have track names and artwork done by hand).
Ripping is a dull job, but it only needs doing once. FLAC (or ALAC if you are Apple oriented) is the way to go, and then downsample or batch conver to MP3. Get it right the first time or you get to re-rip your entire library.