Hello, this is were I will try to remake a few old races and monsters from 3.X for 4E. I'm starting with the Tiefling, because I think that the stats we got now don't really capture the flavour of the old grandchild of a lower planes outsider.
TIEFLING
Average Height: 5' 6''-6' 2'' Average Weight: 140-230 lb.
Ability Scores: +2 Intelligence, +2 Charisma Size: Medium Speed: 6 squares Vision: Low-light
Languages: Common and Abyssal or Infernal Skill Bonuses: +2 Bluff, +2 Stealth Bloodhunt: You gain a +1 racial bonus to attack rolls against bloodied foes. Fiendish Resistance: At 1st level choose either cold, fire or lightning, you get a resistance of 5 + one-half your level against that energy type. Fiendish Heritage: At 1st level you can choose one of the following powers.
Chains of Vengeance Tiefling Racial Power If you get wounded you strike back like a Kyton. Encounter Free Action Melee weapon Special: For using this power you have to hold or wear a spiked chain. Trigger: You become bloodied for the first time in the encounter. Effect: You make two spiked chain attacks.
Cloud of Darkness Tiefling Racial Power A cloud of darkness obscures you, but your vision pierces it. Encounter Minor Action Close burst 1 Effect: This power creates a cloud of darkness, that remains in place until the end of your next turn. The cloud blocks line of sight for all creatures except you. Any creature except you entirely within the cloud is blinded.
Dominating Kiss Tiefling Racial Power With a kiss enhanced by your fiendish powers you dominate the mind of a foe. Encounter Standard Action Melee Target: One creature Attack: Dexterity vs. AC Effect: On a hit make a secondary attack against the same target. Secondary Attack: Charisma vs. Will; if you succeed the target is dominated until the end of your next turn.
The fluff is of course that of our dear old tieflings with horns, strange skin or/and eye colours, rat tails, hooves or whatever they have. 
Since the aasimar too are in the planetouched entry of the old MM I make them now.
AASIMAR
Average Height: 5' 6''-6' 2'' Average Weight: 135-220 lb.
Ability Scores: +2 Wisdom, +2 Charisma Size: Medium Speed: 6 squares Vision: Low-light
Languages: Common and Celestial Skill Bonuses: +2 Insight, +2 Perception Celestial Heritage: At 1st level, you choose an at-will attack power from the paladin class. You can use that power as an encounter power. Celestial Resistance: At 1st level choose either acid, cold or lightning, you get a resistance of 5 + one-half your level against that energy type. Strong Will: You gain a +1 racial bonus to your Will defense and a +2 bonus to your saving throws against fear effects.
Paragon tier feat:
Celestial Affinity
Prerequisite: 11th level, aasimar
Benefit: You can use the power you chose through your Celestial Heritage racial trait as an at-will power.
If you choose the paragon multiclassing option (see the Player’s Handbook, page 209), you can choose powers at 11th level, 12th level, and 20th level from any divine class, instead of only from your second class. You can also use a holy avenger as an implement for all powers with the divine and implement keywords.
So, that's it for today, feel free to review it and make suggestions (not the spell! ) 
But now I'm back and in the process of catching up with the new 4E releases. I just wrote a little update for the aasimar (errata and a feat). Of course this can be added to any conversion projects, that's the reason I posted it here.
I never liked the 3e tiefling, as I'd be more interested in the 2e tiefling for 4e, at least 4e got it right with +2 cha and +2 int which would be closer to a 2e tiefling, but all the special abilities didn't match.
This tiefling is about equivalent to the 4e counterpart in power, which is a good point of reference. Aasimar is fine, though I would say it's a departure from the 3e tiefling, though almost adaptable as the 2e tiefling under the optional rules.