If you haul your bike fewer than two or three times during the summer: Go with a trunk-mounted rack. They're cheap ($60 to $150), they're easy to mount and remove, they store well, and you won't get bugs stuck in your spokes. The downside is you have to remove your bike to get in the trunk, you have to lock the bikes up when you leave the car at rest areas and outlet malls, and in a rear-end collision, your bike may be rendered unridable.
Where to buy: Thule 960 Freeway trunk-mounted bike rack, $65; go to www.thuleracks.com for dealer locations.

If you bring your bike to the beach house nearly every weekend: Go with a roof system. It's expensive (the basic roof-rack package is about $250; the bike rack, from $85 to $120), but it's worth the peace of mind if you're going to be on the road a lot. The most secure way to attach a bike is with a fork-mounted rack, which requires removing the front tire. But for most people, an upright (or wheel-mounted) bicycle rack is the way to go. The downside is that upright racks are not quite as sturdy, because the bike sits high on the roof.
Where to buy: Roofrack components: Q Tower roof rack, $120; two pairs of Q Clips, $48; two 48-inch crossbars, $84; and four SKS Lock Cores, $40 a set. Bike rack: Locklaw bike rack, $85. Total: $377. All from Yakima; go to www.yakima.com for dealer locations.