New Pew Research national survey (June 18-29, 1,574 RV) shows Barack Obama leading John McCain by eight points, a slight widening of his lead over the last month:

Obama 48 (+1 vs. last poll May 21-25)
McCain 40 (-4)
Undecided 12 (+3)

Overall, Obama leads in the RCP National Average by 5.5%.

Other notables: Pew pegs the Generic Congressional Vote at D +15 (52 to 37). For reference, in June '06 Pew had the generic vote at D+12 (51 to 39) and in June of '04 they reported D+7 (48 to 41). Overall, the RCP Average shows Democrats with a 12.2% advantage.