SleepingOverhaul by CosmicDan
Replaces 'skip-to-day' with a realistic time-lapse sleep, among other configurable enhancements.
Sk1er Ranked Projectile Mod by Sk1er
Allows you to have the ranked projectiles without unlocking them. Client-side only!
Fragile Glass and Thin Ice by FredTargaryen
Fragile glass and thin ice blocks which shatter gratuitously on impact! And now, weak stone blocks that fall when you stand on them. Great for adventure maps.
Brick-a-Brac by Saikou
A small mod that adds some decorative blocks to Minecraft. For now, just metal bricks, but there's more on the way soon!
Chemica by noogenesis
A realistic chemical model for Minecraft, manifested in the game through vanilla-like mechanics and a distinct lack of GUIs