Sorry if this was mentioned before on the forum.
I've spent quite some time looking for the best way to convert (mass-convert if possible) fb2 (FictionBook 2.0) ebooks to BBeB and just couldn't find anything convenient or reliable enough. I've tried exporting directly from BookDesigner to LRF, but that just doesn't work like it should all the time and has it's quirks. I even tried copy pasting the rich-text content from BookDesigner into BBeB Binder (something that works wonders for some stubborn RTF and HTML files, BTW).
And then i ran into this:
Seems like lrs2lrf (LRSParser) author made the ultimate FB2 converter for Sony Reader users. It works like a charm, has a nice, minimalistic interface and handles multiple files (folderfulls of them) without a hitch. It converts all the relevant formatting, headings, chapter breaks, the cover... It even puts little book and chapter titles in the header and footer, and manages margins much more wisely than Sony's own ebooks do. A truly wonderful work!
Direct download link: