Hi,
For my own CCNP Switch i was lucky enough to borrow 4x 3560 switches from work.
However, 3x 2950 should take you alot of the way (recommend 3 switches if you want to lab spanning-tree.)
The downside with l2-only switches is that you miss out on HSRP (and VRRP), GLBP and multilayer switching. Atleast the redundancy protocols are very important on the exam, since these tend to be asked in alot of the questions, but a router should do the work in that case.
Good luck.
Kristian Brown