Definitely plenty of pre-made spreadsheets abound, if you google around for them. Blockfolio is really nice (as someone already mentioned) for a routine "snapshot" look but without excruciating maintenance it can be inaccurate for anyone who trades more than a little bit. Also Polo (and I think trex and most of the other major exchanges) allow you to download your trade history as a spreadsheet or CSV so you can easily populate the data for historic P/L views.
Spreadcheets port easily, at least for your viewing pleasure, onto several devices like Android tablets.
And take a look at that URL there are all the most recent "last trade" values inside for each and every coin. Fetch those, multiply with funds hold, sum up the bottomline. You could ask around the freelancers at Bitcointalk if someone would tinker on a CGI that you can host on your own desktop or elsewhere, accessing your portfolio performance by a single click on a bookmark
https://poloniex.com/public?command=returnTicker