You want http://calibre-ebook.com/ its a great piece of software.

Coverts lit individually or in bulk.

Great for managing your books also when you get into the hundreds.

Input Formats: CBZ, CBR, CBC, EPUB, FB2, HTML, LIT, LRF, MOBI, ODT, PDF, PRC**, PDB, PML, RB, RTF, TCR, TXT

Output Formats: EPUB, FB2, OEB, LIT, LRF, MOBI, PDB, PML, RB, PDF, TCR, TXT

So does it all basically.