Another cool B/X edition retro-clone is Old School Essentials.
Old School Essentials (OSE) by Gavin Norman, also known as 'Necrotic Gnome', has reformatted the B/X edition rules into smaller, more modular books. Gavin has combined both the Basic and Expert rules into a single volume called the 'Rules Tome' or as a boxed set of individual books where he organizes each major section into a smaller individual book.
If you are in North America, you can purchase them from a site called Exalted Funeral to reduce the shipping costs.
If you are in Europe or the other side of world, you can purchase them directly from Necrotic Gnome.
NOTE: The original boxed sets are now out-of-print and not available from either store, but new boxed sets are being funded on Kick Starter including brand new cover art from the original 1981 cover artist, Erol Otus.
Old School Essentials stays true to the original B/X edition content, presenting any optional, 'homebrew', or 'house rules' as completely separate books and presents popular new D&D concepts like Ascending Armor Class along side of the traditional Descending Armor Class to serve both preferences.
These books are another great way to introduce new players to the game - offering them an affordable format that new players can all own for themselves.
Cool web reference for free
Gavin also runs a free online version of his interpretation of the B/X rules on his web site to assist new Game Masters (GMs) and players alike.