First of all is Coinbase. Fantastic wallet with to many options and benefits that "I think" don't offer any other bitcoin wallet. I write "I think" because I don't know if this is true because have not knowledge about the qualities of all the bitcoin wallets in the market. At Coinbase all the fees are paid from the wallet, 98% of all bitcoins are saved offline (so no one can do nothing to my coins), all the bitcoins stored on their servers are covered by their insurance policy etc.
The second one is blockchain.info. Offer very qualitative and intuitive easy to understand bitcoin services compared to similar sites. I had even a bitcoin wallet with them at the early beginning of my story with bitcoin. But then move to Coinbase primarily because the fees. At blockchain.info the fees of the sent bitcoins must be paid by me. At Coinbase are paid from Coinbase. Then understood that Coinbase offer even more. The options given above.
The third one is Blocktrail. I don't know very well this site which offer wallet and other services regarding bitcoin. But I like their bitcoin explorer because of particular data that are given (as i know) only by this explorer (for example the catch of a double spent bitcoin). I don't know if blockchain.info give this info but if yes then I cannot give other reasons about the why i like this third site.
Have no other services or business related with bitcoin known by me to be named. Anyhow remain to be at the fourth and fifth place Microsoft and Dell which accept bitcoin as a currency for their products. In some way even those are connected with bitcoin. This is a very good publicity for this coin and help very much in its spread.