Hi. You may use Mfold, RNA structure ... or a soft developed by a friend of mine "assemble" at IBMC (http://bioinformatics.org/assemble/). You may even interact with him if you have any questions ...
Hi Shahed, I would suggest You try with ARWEN, tRNA detection in metazoan mitochondrial sequences,,, or with tRNAscan-SE Search Server http://lowelab.ucsc.edu/tRNAscan-SE/
You might find our RNA Studio helpful http://bibiserv.cebitec.uni-bielefeld.de/bibi/Tools_RNA_Studio.html for predicting secondary structures (even with pseudoknots) via a web submission. For visualization, I'd like to second Leszek and recommend http://varna.lri.fr/