If you don't run a CP an optimized 256mb vps would be more then enough for a 25-30 slot TS server. Since you're also running a small low volume website I would bump it up (more so if you need a CP). What you need to watch out for is the bandwidth use if you use TS alot.
Thanks for the info. It seems that I'd end up being better off getting a cheap shared hosting plan to replace my 1and1 hosting (due to the recent price increase) and simply upgrade the number of slots with my current teamspeak host. I can't imagine I could get those kind of specs for $10/month or less.
You’re probably going to need a dedicated amount of 512mb of ram just to be safe. You can install webmin or a similar control panel that uses small amounts of resources to manage the VPS. Keep in mind that Apache, MySQL and PHP will eat up more ram than you think (around 140mb un optimized). Just a head up, I am unfamiliar with TS but I am sure that you will be able to get by with 512mb dedicated and 784 burstable.
It's tough to to beat the dedicated TS/Vent hosts, you can often get a 25-30 slot server for under $10/mo. But if you want to learn head over to the offers section and you'll find plenty of 128MB-256MB VPS's. Installation is pretty easy there are plenty of guides out there.
I've run LAMP / TS2 and Ventrilo on Debian "Sarge" in the past from my home on a crappy PC built out of spare parts, but I never had to worry about the specs... home broadband (3 mbps/512 kbps) was more than enough to run a Teamspeak or Ventrilo server without issue, but the dynamic IP was a pain to work around and it would tend to reset in the middle of prime time, much to the annoyance of my users. That and I had to cap my torrenting. I was hoping I could save a buck going unmanaged combining the two services and doing it myself, but alas...