Best part, all of these are free.
1. Dropbox – Dropbox is a cloud-based document storage service that, for me, completely replaces my reliance on my work file server. Simply download & install the app and save files to folders on your computer that you designate— just like you would normally do. When you save something, it is synced in the cloud to your Dropbox account and becomes available on any other Dropbox-enabled computer or mobile device. Countless times I’ve been in an airport or at a meeting and had someone request a file and I’ve been able to send it to them right from my iPhone.
https://www.dropbox.com/referrals/NTE4Nzc3NDg5?src=ab_global1
2. Springpad – I just started playing with Springpad yesterday as a Delicious replacement. (Here’s my account, to see how I’m using it.) It takes bookmarking to a whole new level! Springpad allows (and automatically formats) to-do lists, web bookmarks, meeting agendas, photos, recipes & barcodes to products you want to look-up later. Then you can easily organize everything into little buckets which you can easily access from your mobile device or share with friends. I’m constantly bookmarking things for work, blog ideas, teaching illustrations, and even shopping lists… Springpad is amazing at all of this. The best part is that the slick HTML5 interface is fun/easy to use all while storing everything in the cloud. It’s just getting started and I’m thinking it’ll be one of the break-out productivity apps of 2011.
http://springpadit.com/home/;jsessionid=E1446230577ADFBE5178DBC4F2156F29.SPAD_NODE4
3. Evernote – Evernote is my constant companion. With an application for my laptop and one for my phone, I can take notes, store them in the cloud, and access them seamlessly from anywhere I have an internet connection. This is particularly useful in places where my internet connection is a little bit sketchy. Say, on a mission trip in Haiti, or in a convention center for NYWC, or even parts of my church building. I can take notes and have them sync later. If you are looking to take it to the next level there are a whole myriad of plug-ins for Evernote which can make the app even more useful for your specific needs.
https://www.evernote.com/