Delegate Obsession Update [UPDATED Thurs 5/1. 2 PM]
It will take 2,024 delegates to win the nomination. That number goes up and down slightly as superdelegates are added and removed for various reasons.

Article 19 Delegate Projection (current pledged count + superdelegate projection + projection of upcoming states that have been polled)
Barack Obama--2053
Hillary Clinton--1955
(John Edwards--19)
Obama +98

Details below...

Current Pledged Delegate Count [UPDATED Sat. 4/26 3 PM to reflect PA results.]
Obama 1490
Clinton 1336
Obama +154

Current Superdelegate Count (and superdelegate projection, supposing the remaining split evenly)[UPDATED: Thurs 5/1 12 pm]
Obama 244 (389)
Clinton 260 (405)
Clinton +16 (+16)

Projection of upcoming states which have been polled (based on average of 3 recent polls, plus assuming undecideds break for Sen. Clinton 2:1) [UPDATED Thu 5/1 2 PM to reflect new polls in NC and IN.]

NC (115): Obama - 51.2 - 48.8 (59-56) O +3 [O +36k of 1.5m]
WV (28): Clinton - 67 - 33 (19-9) C +10 [C +134k of 400k]
IN (72): Clinton - 55.8 - 44.2 (40-32) C +8 [C +104.4k of 900k]
KY (51): Clinton - 69.9 - 30.1 (36-15) C +21 [C +199k of 500k]
OR (52): Obama - 54 - 46 (28-24) O +4 [O +48k of 600k]
SD (15): Obama - 52.6 - 47.4 (8-7) O +1 [O +4.2k of 100k]
PR (55): Clinton - 58.7 - 41.3 (32-23) C +9 [C +156.6k of 900k]

Obama 174
Clinton 214
Clinton +40
Clinton +505,800

Total (current pledged + projected superdelegate + projected polled states)
Barack Obama--2053
Hillary Clinton--1955
Obama +98

What's left to consider[UPDATED Mon 4/26 3 PM to reflect polling in PR, SD, OR]:
That still leaves 20 pledged delegates yet to be assigned from those yet to vote for which there are no polls: Guam (4) and Montana (16).