According to Barack Obama's presidential website:
Obama Requested $300,000 For The Adler Planetarium & Astronomy Museum. In 2006, Obama requested $300,000 for the Adler Planetarium & Astronomy Museum is seeking to replace and update the planetarium projection system in its original planetarium theater. The current system is approximately 40 years old and nearing the end of its lifespan. Revenues from the show are a significant source of income for the museum, and a new projection system will provide Adler the opportunity to enrich its current sky shows and develop new ones. The goal of this project is to provide world-class educational experiences in the theater, and leverage private contributions by securing federal support for the planetarium.This link also directs you to the rest of Obama's earmarks for the 2006 and 2007 fiscal years.
Update: Uh-oh...did McCain say it was $3 million? The transcript says McCain said, "He voted for nearly $1 billion in pork barrel earmark projects including, by the way, $3 million for an overhead projector at a planetarium in Chicago, Illinois."
Obama's website says $300,000.
Update two: The Washington Times reported last month that Obama submitted two separate requests for the planetarium worth $3.3 million total.
Update three: Here is the correct request McCain was referencing from Barack Obama's Senate website. Obama made this request in fiscal year 2008, on top of the previous $300,000 request.
This is from Obama's Senate website:
Adler Planetarium, to support replacement of its projector and related equipment, $3,000,000 One of its most popular attractions and teaching tools at the Adler Planetarium is the Sky Theater. The projection equipment in this theater is 40 years old, and is no longer supported with parts or service by the manufacturer. It has begun to fail, leaving the theater dark and groups of school students and other interested museum-goers without this very valuable and exciting learning experience.