Few years ago I used Xively to upload my sensor data to, and to visualize the sensor data. What is a good replacement?
This is a personal opinion. I would get a shared webhost account with your own domain name and collect data yourself. You would be in control of the data and do whatever you want. It’s not free to have a webhost account, but for only $40-$75 per year, you can do whatever you want with basically no limitations. A webhost like cleverdot.com allows you to have an account for $40 for the first year w/domain name.
You would have to learn PHP/MySQLi, or have a friend or freelance programmer help you with the scripting. The visualization part could be utilizing Google Charts, or a premade JQuery dashboard.
A big advantage to having your own website would be the ability to create your own APIs where other people or other imps could access your data, or the ability for others to upload data to your website. You would in a sense, be your own Xively.
And of course, you have a website to use for whatever you wish. Maybe it would be a place where you could play around and experiment with other impish things. Or create a blog where you describe your projects.
In the vein of what mlseim proposed, I’m a fan of Python Anywhere. With this service you can use a simple Flask or iPython or Django App/API to get a service going where you can post data. There is a free account, but then some easy to access pricing on paid accounts. Support has been great! Of course this assumes you would want to tinker/setup the cloud app yourself.
If not that, then I like Carriots. Very easy to access. Also great support and I’ve done a couple hobby and commercial projects with them.
If you’re wanting something to very easily give you graphs etc, I’d try initial state. It’s very, very easy to use and has a hoopy web visualisation interface.
If you’re after simple auto updating line charts (similar to Xively) then suggest thingspeak.com.
As there are so options to choose from (see https://electricimp.com/businesssolutions/partners/) I suggest you draw up a list of key requirements to help you narrow it down a bit. For me the first item is always to work out how long you want the data to be kept for. There is always a cost to this, such as having to renew an annual subscription, or otherwise you should at least know the finite lifetime of your data with a free service.