1 Samuel 2:8, 10
The foundations of the earth are the LORD's; upon them he has set the world...the LORD will judge the ends of the earth.
He set the earth on its foundations; it can never be moved.
Isaiah 11:12 (NKJV)
He will set up a banner for the nations, and will assemble the outcasts of Israel, and gather together the dispersed of Judah from the four corners of the earth.
Some points to keep in mind:
1. It's possible that people living during the times these passages were written would have believed the earth was flat, and that God simply spoke to them in terms that they would understand.
2. Often, verses like the ones above are found in poetical passages (see 1 Sam 2:1-10, Ps 104:1-5) that illustrate God's power and sovereignty by using imagery and figures of speech. The purpose of these passages is not to explain scientific principles, but to paint a vivid picture of who God is. In fact, despite our knowledge of astronomy, we continue to use scientifically inaccurate terms and figures of speech today - we speak of sunrises and sunsets, the moon waxing and waning, "the Western world" (what does "west" mean in reference to a rotating sphere?), etc.
Other responses (offsite)