There are so many cool things out there for an older boy to enjoy, but of course, your budget is going to factor in to the equation. Here are a few ideas.
1. Snap Circuits Kits. These can be expensive (the Snap Circuits Lights kit runs around $80) but they are great for any boy that enjoys science and creating things. They also have a lot of "play" potential; the lights kit has around 175 projects that your nephew can enjoy.
2. Lego sets. Lego is usually a big hit with any kid age five and up, so you really can't go wrong with this gift idea. They have a lot of different themes and sets to match any price range. With the new Star Wars movie coming out shortly, one of Lego's buildable Star Wars figures might be the perfect gift for your nephew.
3. Books! There are a lot of cool series that can really stimulate the imagination. Personal favorites in my family are the Percy Jackson series and the Harry Potter series.
4. My Monopoly. This version is a twist on the classic game, where players can customize their tokens, properties and even the Chance and Community Chest cards. Even better, they can change these things up as they see fit, leading to endless fun.