Use PowerPoint to create giant letters in any font. Use pictures, textures, or color to fill to fit any theme. You can also print out on bright paper (and laminate) for cheap and durable bulletin board letters. Great way to have just the letters you need.
Boggle- This is by far the most popular in my room. I got this amazing activity from Create-Teach-Share and my kids go bananas for it. I just change the letters weekly to reflect our spelling pattern focus and they go on a word making frenzy. LOVE it!