Amulet of resist slowing
The amulet of resist slowing was an amulet specifically designed to prevent the slow status effect. In addition, it extended the duration of effects that hasted the player (as it resisted you slowing down from your heightened speed).
The usefulness of these amulets varied by character, from being about on par with an amulet of clarity for spellcasters to being an absolute godsend for berserkers. The amulet prevented the slowness caused by berserking - in effect, it removed most risk caused thereby, giving berserkers free Haste and Might at virtually no cost other than food. Even high-MR non-berserkers would still find the Haste extension useful, though other amulets such as conservation or resist mutation would sometimes have been better in general.
The amulet of resist slowing was replaced in 0.6 with the amulet of stasis. In very ancient versions of Crawl, these were known as amulets of maintain speed.