There are a number of fairly new web applications out there that have caught my attention. Each of them appears to be very useful in its own right but in my opinion if they were all combined into one super product, the whole could indeed be much greater than the sum of the parts. The apps I am referring to are:

• Fuser - all your email and social network messages in one inbox with a pretty nifty interface. Good coverage over at TechCrunch.
• Orgoo - your email, IM and SMS messages in one inbox. 
• Xobni - not currently a web app but a potentially game-changing MS Outlook plug-in that builds a social network around your email. Its killer features for me include having all attachments shared with a contact readily to hand and removing the need to toggle between calendar, mail and tasks. Search is also a big feature, as are a number of others. Best write up so far IMHO is at VentureBeat.
• Lunarr - document centric messaging whereby you attach messages to documents rather than the other way round as is predominantly done with email systems.  I really like the write on the ‘back’ of documents feature. Great summary by Mashable.
• FeedEachOther - nice looking feed reader that recommends similar feeds you may like based on what you read. Also displays comments from feeds unlike most other readers and allows sharing to groups or categories of contacts - e.g. friends, co-workers etc. Good review at Read/WriteWeb.
• coComment - “keeps track of all the online conversations you’re following in one convenient place, and informs you whenever something is added to a conversation”.

It’s a big ask I know, but if a single product could incorporate the primary features of all the above applications and do so in a neat uncluttered interface (allowing users to switch between modes perhaps), then in my view it could be a killer app - the quintessential web 2.0 app that justifies all the hype.

Perhaps Yahoo should consider buying a number of these companies and incorporating their apps with its existing products - Yahoo Mail in particular. Not that such multi-product integration is easily achieved though.

What do you think? Any other products you would want to see built into our Mega App?