Some yes, others no. Sadly HIB has a lot of games that are available DRM-free outside of Steam, but they only provide Steam keys.
Every game in a Humble _Indie_ Bundle has always been available DRM free. Titles in their "Humble Trove" (a monthly subscriber perk) are also DRM free. Other bundles Humble Bundle sells are often Steam only.
I find it slightly sad that Humble Bundle watered down their brand by allowing Steam-only sales in the (Not So) Humble Store, then further by increasingly having Steam-only bundles.