But as long as it's cheap or free, why not build an army of Virtual Private Servers for CPU mining? So I'm listing here some of the services I'm using currently for CPU mining, some of these require CC for validation, some of these doesn't. If you don't have an CC, you can use prepaid Visa CC for most of em. Some even accept Visa Electron's if you're using "Verified by Visa" service on it. I don't know if every bank has this service or not.
Microsoft Azure: (Requires CC / Visa Electron was fine.)
BCN hashrate: ~600 H/s [Using MinerGate GUI for Windows and selected that 16 core A11 CPU from their service. You can do two servers for Microsoft, other is that A11 with 16 Cores [+500h/s] then you can do one with 4 cores. [100-120h/s]
Amazon Web Services: (Requires CC / Visa Electron was fine.)
BCN hashrate: ~50 H/s in Ubuntu while using Miner Gate Command Line.
Google Cloud Computing: (Requires CC / Visa Electron was fine.)
BCN hashrate: ~2400 H/s [Using MinerGate Command Line for Ubuntu, one Virtual Machine gives you 100-120h/s and you can have four of em. Best CPU to use for mining is "n1-standard-2 (2 vCPUs, 7.5 GB memory)" it gives you 20h/s more than others atleast with BCN.] You can have atleast 6 projects with four virtual machines on each. Meaning you can have total amount of 24 virtual machines that each gives you 100-120 h/s
InterServer: ( 0.01$ per VPS slice [Use coupon: 1CENT] / Paypal or CC needed.)
BCN hashrate: ~60 H/s [Using MinerGate Command Line for Ubuntu.]
SoftLayer: (Requires CC)
ElasticHosts: (Requires CC / Visa Electron was fine.)
[i] BCN hashrate: ~30 H/s in Windows Server 2008 while using MinerGate GUI. This is only for 5 days though.
DimensionData: (Might require CC. If it does so Visa Electron was fine.)
BCN hashrate: ~200 H/s with Windows Server 2008 while using MinerGate GUI. I'am running this one: "Win2008 R2 Ent 64-bit with SAP Large PD0 WIN2008R2E/64, 8xCPU, 20480MB RAM, 50GB OS Storage, 350GB Local Storage". Use promotion code: "CSIPCLL02" to get 100$ worth of free use when registering.
CenturyLink: (Might require CC. If it does so Visa Electron was fine.)
BCN hashrate: ~200 H/s with Windows Server 2008 while using MinerGate GUI. You can do 2 servers, one with 4 cpu and one with 2 cpu. 4 CPU ones gives you ~150h/s, 2 Core CPU gives you ~50h/s. You can run them as long as you have something left from that 500$ trial credit.
With my army (11 currently) of Virtual Private Servers I do get an boost of ~2.2kh/s.
There is more than these offering free/cheap trial for VPS, but these are the ones I know and use. If you decide to use some of these or all of em, you're on your own. I'm not taking any responsibility what may happen or does not happen. And this is not being an profitable way for mining, but it offers a little boost to your hashrates for free/cheap for a month or more. If you need help, or have some other questions, just ask. I can't promise that I can help you out, but I will try at least.
[EDIT] Added Hashrates for ByteCoin mining with these services.
[EDIT 2] Added more information about best CPU's to use with Google cloud computing and with Microsoft Azure.
[EDIT 3] Added hashrate of Amazon Web Services free tier. And updated how much I get boost with all my servers mining.
[EDIT 4] Added ElasticHosts.
[EDIT 5 19.12.2015] Added DimensionData.
[EDIT 6 17.06.2017] Added CentyryLink.