Archlich (AP) - Very thematic and good for defensively oriented Artificers.
Archmage (PHB) - Lots of extra dailies and a good revival power. Only for Artificers with multiclass Wizard.
Chosen (PHB, FRPG, DP) - Great features and free pick of several excellent utility powers.
Eternal Seeker (PHB) - Artificers already have a bunch of amazing powers, but the potential of this destiny is high and keeps rising. To get the most out of it, see Litigation's guide.
Lorekeeper (PHB2) - Half-price rituals and a nice damage buff once per encounter, as well as a fairly awesome level 30 ability.
Planeshaper (DDI) - Bonus to Int and an extra use of your favorite encounter power. The utility power gives your entire team a full round of breathing room, which can be a life saver.
Sage of Ages (AP) - Keeper's Prescience is really good. Your Arcana check should be high enough for Trick of Knowledge to be a substantial boost as well.