It's not one mod Sax, but a collection of mods. I seem to recognize bibmod, squeenix (square minimap), ArcHUD (the curved lines around the character for hp/mana), Elkano's BuffBar, Gatherer, Hitsmode, SacredBuff... (might not be the exact ones as there's usually several to do the same thing).
I mainly use CTRA, CT (only for questlevels, timer on casting bar & chat scrolling really), Atlas (map browser), ItemRack (gear switcher), AV Bars (shows timer bars for objectives in AV & AB), BGFlag (shows the name of the FC + can click on it to target), cMinimapCoordinates (shows coordinates on the minimap and main map), Casterstats (shows the amount of +heal/dam, mp5, ... on character sheet) and class/profession specific: Decursive (need it for raids and very handy in PvP), Gatherer (remmebers where you mined/picked flowers, looted a chest), Enchantrix (predicts disenchants), SortEnchant (makes the enchant window sortable by armor type and enchant type), Flexbar (extremely customizable buttons) for Flextotem and on my hunter: AntiDaze (automatically switches off aspect of the cheetah/pack when dazed), MinimapMenu (right click on minimap to set tracking), RangeHelp (indicates wether your target is in range for melee/ranged or in your deadzone) and Beastmaster (sorts pet skills by name).
And bah @ Las as I started messing about with UI mods now :p.