Our company plan to implement XenApp or 2X Application Server in the near future for 30 users using Microsoft Office 2010 Standard, but I have no idea on how to plan the hardware as a host for that configuration, is there anyone here can give me a hint on hardware configuration needed for that purpose f.e processor and memory resources needed
What I would advise is that you use existing tools to estimate the average resource utilisation required for a single user - i.e. min/avg/max CPU, memory and disk/network IO.
Then take this average, multiply it by the current or expected user base, add around 20-40% to account for peak time concurrency (08:30-09:30am and 11:45-13:15pm peaks) then add in another 20-25% for the actual virtualisation overhead and you'll have a series of numbers.
These will be overall Mhz required, max memory required and disk/network IO requirements.
You'll then be able to choose a server with one or more multi-core CPUs (if you can leave yourself space to grow), that can take today what memory you need and also allow for anywhere between 50 and 100% growth over time and has a stable disk controller or SAN capable of creating a RAID 1 or 10 array that'll deliver the throughput you need.
Lastly, and I doubt this will be too much in your case, a network that'll do what you need (I'd imagine a pair of teamed 1Gbps NICs will do all you need).
Then look at your budget and service-availabilty requirements, if you're very techie then you might want to look at supermicro to build your own box, if not just play it safe and buy a HP/IBM/Dell box in whatever form-factor (pizza-box, tower, blade etc.) you want and feel free to come back here to check its specs then.
If I had to put my finger in the air I'd buy a HP DL380 G7 with dual E5640 Xeon CPUs, 12 or 24 GB of memory and 4 x 15k SAS disks - that'll do the job :)